Mom’s genes play a larger role than dad’s in determining whether kids will be obese
A new study finds that kids with obesity are more likely to have obese parents because they inherit obesity-related genes, and to a smaller extent, are impacted indirectly by genes carried by the mother – even when those genes aren’t passed down. A new study led by Liam Wright of the University College London, UK, and colleagues, reports these findings August 5th in the open-access journal PLOS Genetics.
Studies commonly show that children with obesity often have parents with obesity, but the cause of this trend has been poorly understood. Children may inherit genes from their parents that increase their risk of obesity, or they could be shaped by conditions in the womb, or by the food and lifestyle choices their parents make.
In the new study, researchers investigated the effects of the parents’ genetics on the weight and diet of their children. They looked at a measure of obesity called the body mass index (BMI), along with the diet and genetic data from more than 2500 mother-father-child trios. They focused on obesity related genes in the parents – both the ones that were directly passed down to their children, and the genes that weren’t, but that may indirectly impact weight by shaping the child’s environment, which are called genetic nurture effects. They found that, though mothers’ and fathers’ BMIs were consistently correlated with the child’s BMI, this trend could be mostly explained through the genes that children directly inherit. Genetic nurture effects from obesity-related genes in the mother that were not inherited had a smaller impact, only during the child’s adolescence.
The results suggest that a mother’s BMI may be particularly important for determining a child’s BMI, both due to the effects of genes that children directly inherit, and through indirect nurture effects from genes that weren’t passed down. Meanwhile, fathers had little impact on their child’s BMI, apart from the genes that were directly inherited. The study’s authors suggest that analyses that don’t consider the inherited genes are likely to give misleading estimates of the parents’ influence on a child’s weight.
The authors add, “Our results suggest mother’s weight could affect their children’s weight; policies to reduce obesity could have intergenerational benefits.”
Children born to obese mothers are at higher risk of developing metabolic disorders, even if they follow a healthy diet themselves. A new study from the University of Bonn published in the journal Nature offers an explanation for this phenomenon. In obese mice, certain cells in the embryo’s liver are reprogrammed during pregnancy. This leads to long-term changes in the offspring’s metabolism. The researchers believe that these findings could also be relevant for humans.
The team focused on the so-called Kupffer cells. These are macrophages that help protect the body as part of the innate immune system. During embryonic development, they migrate into the liver, where they take up permanent residence. There, they fight off pathogens and break down ageing or damaged cells.
“But these Kupffer cells also act as conductors,” explains Prof Dr Elvira Mass from the LIMES Institute at the University of Bonn. “They instruct the surrounding liver cells on what to do. In this way, they help ensure that the liver, as a central metabolic organ, performs its many tasks correctly.”
Changing the tune: From Beethoven to Vivaldi
It appears, however, that it is this conducting function that is changed by obesity. This is what mouse experiments carried out by Mass in cooperation with other research groups at the University of Bonn suggest. “We were able to show that the offspring of obese mothers frequently developed a fatty liver shortly after birth,” says Dr Hao Huang from Mass’s lab. “And this happened even when the young animals were fed a completely normal diet.”
The cause of this disorder seems to be a kind of “reprogramming” of the Kupffer cells in the offspring. As a result, they send out molecular signals that instruct the liver cells to take up more fat. Figuratively speaking, they no longer conduct one of Beethoven’s symphonies but rather a piece by Vivaldi.
This shift already seems to occur during embryonic development and is triggered by metabolic products from the mother. These activate a kind of metabolic switch in the Kupffer cells and change the way these cells direct liver cells in the long term. “This switch is a so-called transcription factor,” says Mass. “It controls which genes are active in Kupffer cells.”
No fatty liver without the molecular switch
When the researchers genetically removed this switch in the Kupffer cells during pregnancy, the offspring did not develop a fatty liver. Whether this mechanism could also be targeted with medication is still unclear. The teams now plan to investigate this in follow-up studies.
If new treatment approaches emerge from this, it would be good news. The altered behaviour of the Kupffer cells likely has many negative consequences. Fat accumulation in the liver, for example, is accompanied by strong inflammatory responses. These can cause increasing numbers of hepatocytes to die and be replaced with scar tissue, resulting in fibrosis. At the same time, the risk that hepatocytes degenerate and become cancerous increases.
“It is becoming ever more evident that many diseases in humans already begin at a very early developmental stage,” says Mass, who is also spokesperson for the transdisciplinary research area “Life & Health” and a board member of the “ImmunoSensation2” Cluster of Excellence at the University of Bonn. “Our study is one of the few to explain in detail how this early programming can happen.”
Intermittent energy restriction, time-restricted eating and continuous energy restriction can all improve blood sugar levels and body weight in people with obesity and type 2 diabetes, according to a study being presented Sunday at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco, Calif.
“This study is the first to compare the effects of three different dietary interventions intermittent energy restriction (IER), time-restricted eating (TRE) and continuous energy restriction (CER) in managing type 2 diabetes with obesity,” said Haohao Zhang, PhD, chief physician at The First Affiliated Hospital of Zhengzhou University in Zhengzhou, China.
Although researchers identified improved HbA1c levels, and adverse events were similar across the three groups, the IER group showed greater advantages in reducing fasting blood glucose, improving insulin sensitivity, lowering triglycerides, and strengthening adherence to the dietary interventions.
“The research fills a gap in directly comparing 5:2 intermittent energy restriction with a 10-hour time-restricted eating in patients with obesity and type 2 diabetes. The findings provide scientific evidence for clinicians to choose appropriate dietary strategies when treating such patients,” Zhang says.
Zhang and colleagues performed a single-centre, randomised, parallel-controlled trial at the First Affiliated Hospital of Zhengzhou University from November 19, 2021 to November 7, 2024.
Ninety patients were randomly assigned in a 1:1:1 ratio to the IER, TRE or CER group, with consistent weekly caloric intake across all groups. A team of nutritionists supervised the 16-week intervention.
Of those enrolled, 63 completed the study. There were 18 females and 45 males, with an average age of 36.8 years, a mean diabetes duration of 1.5 years, a baseline BMI of 31.7kg/m², and an HbA1c of 7.42%.
At the end of the study, there were no significant differences in HbA1c reduction and weight loss between the IER, TRE and CER groups. However, the absolute decrease in HbA1c and body weight was greatest in the IER group.
Compared to TRE and CER, IER significantly reduced fasting blood glucose and triglycerides and increased the Matsuda index, a measure of whole-body insulin sensitivity. Uric acid and liver enzyme levels exhibited no statistically significant changes from baseline in any study group.
Two patients in the IER group and the TRE group, and three patients in the CER group, experienced mild hypoglycemia.
The IER group had the highest adherence rate (85%), followed by the CER group at 84% and the TRE group at 78%. Both the IER and CER groups showed statistically significant differences compared with the TRE group.
Zhang said these findings highlight the feasibility and effectiveness of dietary interventions for people who have obesity and type 2 diabetes.
A healthy lifestyle has important benefits, but weight alone might not give an adequate picture of someone’s health, say experts
Source: Pixabay CC0
Focusing solely on achieving weight loss for people with a high body mass index (BMI) may do more harm than good, argue experts in The BMJ.
Dr Juan Franco and colleagues say, on average, people with high weight will not be able to sustain a clinically relevant weight loss with lifestyle interventions, while the potential harms of weight loss interventions, including the reinforcement of weight stigma, are still unclear.
They stress that a healthy lifestyle has important benefits, but that weight alone might not give an adequate picture of someone’s health, and say doctors should provide high quality, evidence based care reflecting individual preferences and needs, regardless of weight.
Lifestyle interventions that focus on restricting an individual’s energy intake and increasing their physical activity levels have for many decades been the mainstay recommendation to reduce weight in people with obesity, explain the authors.
However, rigorous evidence has indicated that these lifestyle interventions are largely ineffective in providing sustained long term weight loss and reducing cardiovascular events (eg, heart attacks and strokes) or death.
Even though a healthy lifestyle provides important benefits, acknowledging that weight alone might not give an adequate picture of someone’s health, and recognising the limitations of lifestyle interventions for weight loss, could pave the way for more effective and patient centred care, they say.
Focusing on weight loss might also contribute to societal weight bias – negative attitudes, assumptions, and judgments about people based on their weight – which may not only have adverse effects on mental health but may also be associated with disordered eating, the adoption of unhealthy habits, and weight gain, they add.
They point out that recent clinical guidelines reflect the growing recognition that weight is an inadequate measure of health, and alternative approaches, such as Health at Every Size (HAES), acknowledge that good health can be achieved regardless of weight loss and have shown promising results in improving eating behaviours.
While these approaches should be evaluated in large clinical trials, doctors can learn from them to provide better and more compassionate care for patients with larger bodies, they suggest.
“Doctors should be prepared to inform individuals seeking weight loss about the potential benefits and harms of interventions and minimise the risk of developing eating disorders and long term impacts on metabolism,” they write. “Such a patient centred approach is likely to provide better care by aligning with patient preferences and circumstances while also reducing weight bias.”
They conclude: “Doctors’ advice about healthy eating and physical activity is still relevant as it may result in better health. The main goal is to offer good care irrespective of weight, which means not caring less but rather discussing benefits, harms, and what is important to the patient.”
For many, fitness trackers have become indispensable tools for monitoring how many calories they’ve burned in a day. But for those living with obesity, who are known to exhibit differences in walking gait, speed, energy burned and more, these devices often inaccurately measure activity – until now.
Scientists at Northwestern University have developed a new algorithm that enables smartwatches to more accurately monitor the calories burned by people with obesity during various physical activities.
The technology bridges a critical gap in fitness technology, said Nabil Alshurafa, whose Northwestern lab, HABits Lab, created and tested the open-source, dominant-wrist algorithm specifically tuned for people with obesity. It is transparent, rigorously testable and ready for other researchers to build upon. Their next step is to deploy an activity-monitoring app later this year that will be available for both iOS and Android use.
“People with obesity could gain major health insights from activity trackers, but most current devices miss the mark,” said Alshurafa, associate professor of behavioral medicine at Northwestern University Feinberg School of Medicine.
Current activity-monitoring algorithms that fitness trackers use were built for people without obesity. Hip-worn trackers often misread energy burn because of gait changes and device tilt in people with higher body weight, Alshurafa said. And lastly, wrist-worn models promise better comfort, adherence and accuracy across body types, but no one has rigorously tested or calibrated them for this group, he said.
“Without a validated algorithm for wrist devices, we’re still in the dark about exactly how much activity and energy people with obesity really get each day — slowing our ability to tailor interventions and improve health outcomes,” said Alshurafa, whose team tested his lab’s algorithm against 11 state-of-the-art algorithms designed by researchers using research-grade devices and used wearable cameras to catch every moment when wrist sensors missed the mark on calorie burn.
The findings will be published June 19 in Nature Scientific Reports.
The exercise class that motivated the research
Alshurafa was motivated to create the algorithm after attending an exercise class with his mother-in-law who has obesity.
“She worked harder than anyone else, yet when we glanced at the leaderboard, her numbers barely registered,” Alshurafa said. “That moment hit me: fitness shouldn’t feel like a trap for the people who need it most.”
Algorithm rivals gold-standard methods
By using data from commercial fitness trackers, the new model rivals gold-standard methods of measuring energy burn and can estimate how much energy someone with obesity is using every minute, achieving over 95% accuracy in real-world situations. This advancement makes it easier for more people with obesity to track their daily activities and energy use, Alshurafa said.
How the study measured energy burn
In one group, 27 study participants wore a fitness tracker and metabolic cart – a mask that measures the volume of oxygen the wearer inhales and the volume of carbon dioxide the wearer exhales to calculate their energy burn (in kilocalories/kCals) and resting metabolic rate. The study participants went through a set of physical activities to measure their energy burn during each task. The scientists then looked at the fitness tracker results to see how they compared to the metabolic cart results.
In another group, 25 study participants wore a fitness tracker and body camera while just living their lives. The body camera allowed the scientists to visually confirm when the algorithm over- or under-estimated kCals.
At times, Alshurafa said he would challenge study participants to do as many pushups as they could in five minutes.
“Many couldn’t drop to the floor, but each one crushed wall-pushups, their arms shaking with effort,” he said, “We celebrate ‘standard’ workouts as the ultimate test, but those standards leave out so many people. These experiences showed me we must rethink how gyms, trackers and exercise programs measure success – so no one’s hard work goes unseen.”
Health workers have long relied on Body Mass Index as a way to measure whether people are within a healthy weight range. Now, a collection of top researchers have made the case for a new way to understand and diagnose obesity. In part two of this special Spotlight series, we take a look at what this new framing might mean for South Africa.
If we are going to tackle the global rise in obesity, our understanding of the condition needs to change. That is according to a Lancet Commission convened by a global group of 58 experts from different medical specialties. While we have historically thought of obesity as a risk factor for other diseases like diabetes, the commission’s recent report published in the journal Lancet Diabetes and Endocrinology concludes that obesity is sometimes better thought of as a disease itself – one that can directly cause severe health symptoms (see part one of this series for a detailed discussion of this argument).
By categorising obesity as a disease, public health systems and medical aid schemes around the world would be more likely to cover people for weight-loss drugs or weight-loss surgery, according to the report. At present, these services are often only financed if a patient’s obesity has already led to other diseases. This is given that obesity is not viewed as a stand-alone chronic illness.
But if we’re going to redefine obesity as a disease, or at least some forms of it, then we need good clinical definitions and ways to measure it. For a long time, this has posed challenges, according to the Lancet report.
The perils of BMI
At present, health workers often rely on Body Mass Index (BMI) to gauge whether a patient is within a healthy weight range. BMI is measured by taking a person’s weight in kilograms and dividing it by their height in meters squared.
A healthy weight is typically considered to be between 18.5 and 25. A person whose BMI is between 25 and 30 is considered to be overweight, while someone with a BMI of over 30 is considered to have obesity. But according to the Lancet report, this is a crude measure, and one which provides very little information about whether a person is actually ill.
One basic issue is that a person can have a high BMI even if they don’t have a lot of excess fat. Instead, they may simply have a lot of muscle or bone. Indeed, the report notes that some athletes are in the obese BMI range.
Even when a high BMI does indicate that a person has obesity, it still doesn’t tell us where a person’s fat is stored and this is vital medical information. If excess fat is stored in the stomach and chest, then it poses more severe health risks than when it is stored in the limbs or thighs. This is because excess fat will do more harm if it surrounds vital organs.
The lead author of the Lancet report, Professor Frances Rubino, says that the pitfalls of BMI have long been understood, but practitioners have continued to use it.
“BMI is still by and large the most used approach everywhere, even though medical organisations have [raised issues] for quite some time,” he tells Spotlight.
“The problem is that even when we as individuals or organisations say BMI is no good, we haven’t provided an alternative. And so, inevitably, the ease of calculating BMI and the uncertainties about alternatives makes you default back to BMI.”
To deal with this problem, the report advocates for several alternative techniques for measuring obesity which offer more precision.
The first option is to use tools that directly measure body composition like a DEXA scanner. This is a sophisticated x-ray machine which can be used to distinguish between fat, bone and muscle. It can also be used to determine where fat is concentrated. It’s thus a very precise measurement tool, but the machines are expensive and the scans can be time-consuming.
Alternatively, the report recommends using BMI in combination with another measure like waist-to-hip ratio, waist-to-height ratio or simply waist circumference. If two of these alternative measures are used, then BMI can be removed from the picture.
These additional metrics are clinically useful because they provide information about where fat is stored. For instance, a larger waistline inevitably indicates a larger stomach. Indeed, studies have found that above a certain level, a larger waist circumference is linked to a higher chance of dying early, even when looking at people with the same BMI.
The report thus offers a more accurate way to measure obesity in the clinical setting. But its authors argue that this is only the first step when making a diagnosis. The second is to look at whether a patient’s obesity has actually caused health problems as this isn’t automatically the case. They acknowledge for instance that there are some people with obesity who “appear to be able to live a relatively healthy life for many years, or even a lifetime”.
The report refers to these cases as “preclinical obesity”. Such patients don’t have a disease as such, according to the report, but still have an increased risk of facing health issues in the future. As such, the report’s authors argue that they should be monitored and sometimes even treated, depending on factors like family history.
By contrast, cases of obesity which have directly caused health problems are referred to as “clinical obesity”. These cases, according to the report, should be treated immediately just like any other serious disease. It lists a series of medical symptoms associated with clinical obesity that would allow health workers to make an appropriate diagnosis.
The recommendation is thus for health workers to determine whether a person has obesity through the metrics listed above, and then to determine whether it is clinical or preclinical by evaluating a patient’s symptoms. This will inevitably guide the treatment plan.
How does this relate to SA?
Professor Francois Venter, who runs the Ezintsha research centre at WITS university, says the Lancet report offers a good starting point for South Africa, but it has to be adapted for our own needs and context.
“It’s a big step forward from BMI which grossly underdiagnoses and overdiagnoses obesity,” says Venter, who adds that additional metrics like waist circumference are a “welcome addition”.
The view that clinical obesity is a disease that needs to be immediately treated is also correct, according to Venter. Though he adds that the public health system in South Africa is not in a financial position to start handing out weight-loss medicine to everyone who needs it.
“The drugs are hugely expensive,” says Venter, “and they have side effects, so you need a lot of resources to support people taking them.” But while it may not yet be feasible to treat all cases of clinical obesity in South Africa, Venter believes we should use the diagnostic model offered by the Lancet Commission to begin identifying at least some people with clinical obesity so that they can begin treatment.
“You have to start somewhere, and for that you need a good staging system,” he says. “Let’s use the Lancet Commission and start to see if we can identify a few priority people and screen them and start to work on the drug delivery system.”
Yet while Venter believes that the commission makes important contributions, he also cautions that we need more data on obesity in Africa before we can apply all of its conclusions to our own context.
“If you go to the supplement of the Lancet Commission, there’s not a single African study there. It all comes from Europe, North America and Asia. It’s not the commission’s fault but [there is a lack of data on Africa].”
This is important as findings that apply to European or Asian populations may not necessarily hold for others. Consider the following case.
As noted, the commission states that BMI is not sufficient to determine whether someone is overweight and must therefore be complemented with other measures. But it states that if someone’s BMI is above 40 (way above the current threshold for obesity), then this can “pragmatically be assumed” without the need for further measures.
But this may not hold in Africa, says Venter.
“The commission says that if your BMI is over 40, which is very big, you can infer that this person has got obesity and they are sick and need to lose weight. I don’t know if we can say that in Africa, where we often have patients who are huge, and yet they are very active, and when you [look at] their blood pressure and all their metabolics, they’re actually pretty healthy,” he notes. “So, I think they’re sometimes jumping to conclusions about African populations that we don’t have data on,” adds Venter.
Is South Africa ready to move past BMI?
Another concern is that while the Lancet Commission may offer useful recommendations for advanced economies, its starting assumptions may not be as relevant for countries like South Africa.
For instance, while specialists agree that BMI is a crude measure of obesity, direct measures like DEXA scans are “out of our reach economically”, according to Professor Susan Goldstein, who leads PRICELESS-SA, a health economics unit at the South African Medical Research Council.
And while supplementing BMI with the other metrics like waist circumference may be doable, health experts told Spotlight that at present healthcare workers in South Africa aren’t even measuring BMI alone.
Dr Yogan Pillay, a former deputy director-general at the national health department who now runs TB and HIV delivery at the Gates Foundation, told Spotlight: “I can’t tell you how few people in the public sector have their BMI monitored at all. Community health workers are supposed to be going out and measuring BMI, but even that’s not happening”.
Goldstein also suggests that the monitoring of BMI in South Africa is limited. “If you go into the clinic for your blood pressure, do they say: ‘How’s your BMI?’ No, I doubt that,” says Goldstein. “It’s just not one of the measures that [gets done].”
She adds that South Africa could introduce the combination of metrics proposed by the commission, like waist circumference combined with BMI, but says it would simply require “a lot of re-education of health workers”.
Prevention vs treatment
For Goldstein, the commission is correct to regard clinical obesity as a disease which needs to be treated, but we also shouldn’t view medication as the only way forward.
“We have to remember that prevention is very important,” says Goldstein. “We have to focus on food control, we have to look at ultra-processed foods, and unless we do that as well [in addition to medication] we are going to lose this battle.”
The National Health Department already has a strategy document for preventing obesity, but some of its recommendations have been critiqued for focusing on the wrong problems. For instance, to prevent childhood obesity, the strategy document recommends reforming the Life Orientation curriculum and educating tuck shop vendors so that both students and food sellers have more information about healthy eating. But as Spotlight previously reported, there are no recommendations to subsidise healthy foods or to increase their availability in poor areas, which several experts believe is more important than educational initiatives.
Venter also highlights the importance of obesity prevention, though he emphasises that this shouldn’t be in conflict with a treatment approach – instead, we need to push for both.
“The [prevention] we need to do is fix the food supply… and the only way you do that is to decrease the cost of unprocessed food.” But while this may help prevent future cases of obesity, it doesn’t help people who are already suffering from obesity, says Venter. And since such people comprise such a large share of the population, we can’t simply ignore them, he says.
“Even if you fix the entire food industry tomorrow, those [people who are already obese] are going to remain where they are because simply changing your diet isn’t going to do diddly squat [when you already have obesity],” he adds. (Part 1 discusses this in more detail).
Goldstein adds that increasing access to treatment would also inevitably reduce the costs of “hypertension, diabetes, osteoarthritis, and a whole range of other illnesses if it’s properly managed”.
One way to advance access to medication would be for the government to negotiate reduced prices of GLP-1 drugs, she says. (Spotlight previously reported on the prices and availability of these medicines in South Africa here.)
Funding
A final concern that has been raised about the Lancet commission is about its source of funding.
“I don’t know how one gets around this,” says Goldstein, “but there were 58 experts on the commission, 47 declared conflicts of interest.”
Indeed, the section of the commission that lists conflicts of interest spans over 2 000 words (roughly the size of this article). This includes research grants and consulting fees from companies like Novo Nordisk and Eli Lilly, which produce anti-obesity drugs.
In response, Rubino told Spotlight that “people who work in the medical profession obviously work and consult, and the more expertise they have, the more likely they are to be asked by somebody to advise. So sometimes people have contracts to consult a company – but that doesn’t mean that they necessarily make revenue if the company has better sales. You get paid fees for your services as a consultant”.
Rubino says this still has to be declared as it may result in some bias, even if it is unconscious, but “if you wanted to have experts who had zero relationship [to companies] of any sort then you might have to wonder if there is expertise available there… the nature of any medical professional is that the more expertise they have, the more likely that they have engaged in work with multiple stakeholders”.
For Venter, there is some truth to this. “It’s very difficult to find people in the obesity field that aren’t sponsored by a drug company,” he says. “Governments don’t fund research… and everyone else doesn’t fund research. Researchers go where the research is funded.”
This doesn’t actually solve the problem, says Venter, as financing from drug companies can always influence the conclusions of researchers. It simply suggests that the problem is bigger than the commission. Ultimately, he argues that the authors should at least be applauded for providing such granular details about conflicts of interest.
Rubino adds that while researchers on the commission may have historically received money from drug companies for separate research studies or consulting activities, none of them received money for their work on the commission itself.
“This commission has been working for more than four years since conception… An estimate of how many meetings we had is north of 700, and none of us have received a single penny [for doing this],” he says.
Disclosure: The Gates Foundation is mentioned in this article. Spotlight receives funding from the Gates Foundation but is editorially independent – an independence that the editors guard jealously. Spotlight is a member of the South African Press Council.
Eating a high-fat diet containing a large amount of oleic acid – a type of fatty acid commonly found in olive oil – could drive obesity more than other types of dietary fats, according to a study published in the journal Cell Reports.
The study found that oleic acid, a monounsaturated fat associated with obesity but also tentatively linked to cardiovascular benefits and often touted as a ‘healthy’ fatty acid, causes the body to make more lipid cells. By boosting a signalling protein called AKT2 and reducing the activity of a regulating protein called LXR, high levels of oleic acid resulted in faster growth of the precursor cells that form new lipid cells.
“We know that the types of fat that people eat have changed during the obesity epidemic. We wanted to know whether simply overeating a diet rich in fat causes obesity, or whether the composition of these fatty acids that make up the oils in the diet is important. Do specific fat molecules trigger responses in the cells?” said Michael Rudolph, PhD, assistant professor of biochemistry and physiology at the University of Oklahoma College of Medicine.
Rudolph and his team fed mice a variety of specialised diets enriched in specific individual fatty acids, including those found in coconut oil, peanut oil, milk, lard and soybean oil. Oleic acid was the only one that caused the precursor cells that give rise to fat cells to proliferate more than other fatty acids.
“You can think of the fat cells as an army,” Rudolph said. “When you give oleic acid, it initially increases the number of ‘fat cell soldiers’ in the army, which creates a larger capacity to store excess dietary nutrients. Over time, if the excess nutrients overtake the number of fat cells, obesity can occur, which can then lead to cardiovascular disease or diabetes if not controlled.”
Unfortunately, it’s not quite so easy to isolate different fatty acids in a human diet. People generally consume a complex mixture if they have cream in their coffee, a salad for lunch and meat and pasta for dinner. However, Rudolph said, there are increasing levels of oleic acid in the food supply, particularly when access to food variety is limited and fast food is an affordable option.
“I think the take-home message is moderation and to consume fats from a variety of different sources,” he said. “Relatively balanced levels of oleic acid seem to be beneficial, but higher and prolonged levels may be detrimental. If someone is at risk for heart disease, high levels of oleic acid may not be a good idea.”
Authors of a recent Lancet report argue that obesity should not just be seen as a risk factor for other diseases – but in some cases, should be seen as a disease itself. The position could change how we treat obesity globally. In the first of this two-part Spotlight series, we break down the debate around the issue, and its implications for health policy.
In 1990, just 2% of all young people around the world aged 5 to 24 were living with obesity. By 2021, this figure had more than tripled to over 6%. This is according to a recent study, which relied on Body Mass Index (BMI) data from 180 countries and territories around the world. It estimates that the rise in obesity among children and young people will only continue in the coming decades.
South Africa certainly isn’t immune to the crisis. A survey conducted in 2021/2022 found that 16% of all children aged 6 to 18 were “severely overweight”. Meanwhile, World Health Organization (WHO) data suggests that about 30% of all adults in South Africa are living with obesity, meaning a BMI of over 30, which is almost double the global level.
BMI, which simply looks at a person’s weight in relation to their height, is a crude measure of obesity. For instance, a person may have a high BMI simply because they have a lot of muscle rather than fat. But while it is agreed that BMI is a flawed indicator at the individual level, many experts recommend using it as a rough proxy for “health risk at a population level”.
For instance, a study which collected data on nearly three million people found that those who had very high BMI levels were, on average, more likely to die at an early age. The study also found that this was true of people with very low BMI levels (those who were underweight). In this context, the above figures paint a concerning picture.
Given the rising rates, experts argue that we need health systems to be able to track and respond to obesity urgently. But, according to a Lancet Commission published in January, health systems around the world may struggle to do this, because of a failure to accurately conceptualise and measure what obesity actually is.
The Lancet commission was developed by 58 experts from different medical specialties and though it has been the subject of debate, it has since been widely endorsed as a new way to understand obesity. Spotlight takes a look at what it concluded.
Delaying treatment for no reason
Obesity is often regarded as a risk factor for other diseases, for instance, type 2 diabetes. But according to the commission, there are certain cases in which obesity is not just a risk factor, but a disease itself – one that should be immediately treated.
One of the reasons for this is that obesity not only contributes to the emergence of other conditions but sometimes leads to clinical symptoms directly. For example, the cartilage that protects the joints in a person’s knees can sometimes become eroded when adults carry too much weight. In this case, a person could suffer from joint pain, stiffness and reduced mobility where obesity is clearly the cause.
Take another example. If fat deposits build up in the abdomen, this may limit how much the lungs can expand, causing breathlessness. Similarly, a build-up of fat around the neck can narrow a person’s upper airways, which can cause sleep apnoea.
Thus, obesity is not simply something which increases the risk of developing a separate disease in the future – but something which can directly (and presently) affect the functioning of organs.
More broadly, the commission argues that by hindering a person’s “mobility, balance and range of motion” obesity can in certain cases “restrict routine activities of daily living”. In these instances, obesity is a disease by definition, according to the commission. This is given that it defines disease as a “harmful deviation from the normal structural or functional state of an organism, associated with specific signs and symptoms and limitations of daily activities”.
But why does this conceptual debate matter?
Because at present, people often have to wait for other diseases to crop up before insurers or public health systems cover them for weight loss drugs or bariatric surgery – a procedure to help with weight loss and improve obesity-related health conditions. And when they do cover these services, it is often only after severe delay. Because obesity is only considered to be a risk factor, it isn’t typically treated with the same urgency as life-threatening diseases, according to the authors of the commission.
Professor Frances Rubino, the lead author of the commission, details how this problem manifests in the healthcare system.
“I’ve been doing bariatric surgery for 25 years in four different countries; in America, Italy, France and the UK,” he tells Spotlight, “In all of those countries, to meet the criteria for surgery people very often have to undergo six to 12 months of weight monitoring before their surgery is covered. So systematically you delay treatment”.
He continues: “Someone who has clinical obesity and has heart failure as a result of it is waiting for a year for what reason? That condition will only worsen and if the patient is still alive, the treatment [is] going to cost the same amount to the payer but it’s going to be less effective.”
Can’t people just diet?
One of the reasons that some academics have historically been reluctant to classify obesity as a disease is because of a fear that this may reduce people’s agency – instead of taking proactive steps to diet and exercise, people with obesity may simply view themselves as afflicted by a disease.
The belief that people with obesity can simply diet their way out of their situation is in fact partially why Rubino’s patients were forced to wait long periods of time before receiving bariatric surgery.
Rubino explains: “In America, many private payers [i.e. medical insurance schemes] have required weight monitoring programmes, where patients do nothing else other than see a dietician for 12 months, and if they skip one appointment, they have to start all over again. I think that in some cases, this has been misguided by the idea that you want to see if obesity can be reversed by somebody going on a diet.”
This, according to him, is a “misconception”, arguing that if someone faces such severe levels of obesity that they require surgery, diet is unlikely to offer a solution.
Indeed, research has shown that it’s very rare for people with obesity to lose large amounts of weight quickly without surgery or medication. For instance, a study on over 176 000 patients in the UK found that among men with “simply obesity” or a BMI of 30-34.9, only 1 in 210 were able to achieve a “normal” weight level within a year. Among men with morbid obesity or BMI of 35 or more, the chance was less than 1 than in 1000. Chances for women were roughly twice as good as men’s – so still exceedingly small.
Thus, if someone is severely obese and their excess weight is causing life-threatening symptoms, putting them on a diet for a year is unlikely to result in the urgent changes that may be required for them to get better. In fact, Rubino argues that they may simply die of their condition in the interim.
Taking a medical approach more quickly is easier now than ever before due to the regulatory approval of GLP-1 agonists like semaglutide and tirzepatide – Spotlight previously reported on the availability of these new diabetes and weight loss medicines in South Africa. An article by WHO officials from December states that because of the approval of these medicines “[h]ealth systems across the globe now may be able to offer a treatment response integrated with lifestyle changes that opens the possibility of an end to the obesity pandemic”.
Not all people with obesity are ill
There is a more scientific argument against categorising obesity as a disease. This is that while obesity can sometimes result in the negative health symptoms discussed above (like respiratory issues or reduced mobility) it doesn’t always do this.
In fact, the commission acknowledges that some people with obesity “appear to be able to live a relatively healthy life for many years, or even a lifetime”. One of the reasons for this is that excess fat may be stored in areas that don’t surround vital organs. For instance, if fat is stored in the limbs, hips, or buttocks, then this may cause less harm than if it is stored in the stomach.
Since obesity doesn’t always cause health problems, it isn’t always a disease. In order to deal with this conceptual hurdle, the commission classifies obesity into two categories – clinical and preclinical obesity.
If a person has pre-clinical obesity, this means they have a lot of excess fat, but no obvious health problems that have emerged as a result. In this case, obesity is not classified as a disease, though it may still increase the chance of future health problems (depending on a range of factors, like family history).
For a person to have clinical obesity, they must have a lot of excess fat as well as health problems that have already been directly caused by this. It is this that the commission defines as a disease.
This classification system, according to Rubino, ensures not only that we urgently treat people living with clinical obesity, but also that we don’t overtreat people – since if a person falls into the pre-clinically obese group, then they may not need treatment.
But if we’re going to treat clinical obesity as a disease, we’ll need clear methods of diagnosing people. Since BMI is deeply flawed and provides little information about whether a person is ill at the individual level, health systems will need something else. In part 2 of this Spotlight special series, we’ll discuss the options offered by the commission, and how this all relates to the situation in South Africa.
New research from the University of Sydney reveals that obesity, having a knee injury and occupational risks such as shift work and lifting heavy loads are primary causes of knee osteoarthritis.
The study also found that following a mediterranean diet, drinking green tea and eating dark bread could reduce the risk of developing knee osteoarthritis.
Using data from 131 studies conducted between 1988 to 2024, the researchers examined over 150 risk factors in participants ranging from 20 to 80 years old to determine which were associated with an increased risk of developing knee osteoarthritis.
“Our research found that while factors such as eating ultra-processed foods and being overweight increase the risk, addressing lifestyle factors – such as losing weight or adopting a better diet – could significantly improve people’s health,” Associate Professor Abdel Shaheed said.
Co-author Professor David Hunter, a researcher at the Kolling Institute and Professor of Medicine at the University of Sydney, said: “Women were twice as likely to develop the condition than men, and older age was only mildly associated with increased risk.”
Reducing the risk of knee osteoarthritis
Dr Duong, lead author and post-doctoral researcher at the Kolling Institute, said: “Eliminating obesity and knee injuries combined could potentially reduce the risk of developing knee osteoarthritis by 14 percent across the population.
“We urge governments and the healthcare sector to take this seriously and to implement policy reforms that address occupational risks, subsidise knee injury prevention programs, and promote healthy eating and physical activity to reduce obesity.”
Study links higher body mass index at various ages across adulthood with greater risks of developing different types of kidney cancer.
Photo by I Yunmai on Unsplash
Excess weight in mid-life is a known risk factor for kidney cancer, but new research indicates that weight patterns throughout life may also affect an individual’s likelihood of developing this malignancy. The findings are published by Wiley online in CANCER, a peer-reviewed journal of the American Cancer Society.
To assess weight patterns and their associations with kidney cancer and its different subtypes, investigators analysed data from 204 364 individuals from the NIH-AARP Diet and Health Study, including body mass index (BMI) data when participants entered the study (an average age of 61.6 years), and prior BMI recordings at 18, 35, and 50 years of age. The team noted that there were 1,425 cases of kidney cancer, or renal cell carcinoma (RCC), among the study’s participants, with 583 having aggressive RCC and 339 having fatal RCC. The researchers also recorded the different subtypes of RCC, including clear cell RCC (541 patients), papillary RCC (146 patients), and chromophobe RCC (64 patients).
Higher BMI at any of the ages assessed was linked with higher risks of overall RCC and all subtypes (except chromophobe RCC), with a 10-40% higher risk for each 5-unit increase in BMI. Similar increased risks were linked to weight gain during adulthood that resulted in overweight or obesity, compared with maintaining normal BMI.
Also, long-term excess weight was associated with higher risks of overall RCC, aggressive RCC, fatal RCC, and clear cell RCC, but not papillary RCC and chromophobe RCC. Weight loss in which BMI was reduced by at least 10%, particularly later in life, was associated with a lower risk of RCC. Specifically, weight loss from age 18–35 years and after age 50 years was associated with 21% and 28% reductions in RCC incidence, respectively.
“These findings emphasise that maintaining a healthy weight across one’s lifetime is important for reducing RCC risk. More importantly, weight loss, even later in life, may offer protective benefits,” said lead author Zhengyi Deng, PhD, of Stanford University School of Medicine. “We should support initiatives that promote healthy weight maintenance and weight loss strategies. Some of these include lifestyle interventions, weight-loss programs, and emerging medical treatments for obesity; however, individuals should consult with their healthcare providers prior to initiation of any plan.”
