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Categories : Metabolic DisordersTags : 19/6/25obesitySouth AfricaSpotlight

The Way We Understand Obesity is Changing: What Does it Mean for South Africa?

On June 19, 2025June 19, 2025 By ModernMedia

By Jesse Copelyn

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.

Republished from Spotlight under a Creative Commons licence.

Read the original article.