Tag: low-carb diet

Categories : Diet and NutritionTags :

Intermittent Fasting: Is it the Calories or Carbs that Count?

On By ModernMedia
Photo by Ayako S

Adam Collins, University of Surrey

Intermittent fasting is not only a useful tool for weight loss, it’s also shown to have many benefits for metabolic health – independent of weight loss. Yet many people may find intermittent fasting to be a challenge, especially if following the 5:2 version of the diet where calories are severely restricted two days a week.

But my latest study shows that you don’t need to severely restrict your calories to get the metabolic benefits of intermittent fasting. Even just restricting the number of carbs you eat twice a week may be enough to improve your metabolic health.

Intermittent fasting appears to be so beneficial for health because of the way it alters our metabolism.

After a meal, our body enters the postprandial state. While in this state, our metabolism pushes our cells to use carbohydrates for immediate energy, while storing some of these carbs as well as fat for later use. But after several hours without food, in the postabsorptive “fasted” state, our metabolism switches to using some of our fat stores for energy.

In this regard, intermittent fasting ensures a better balance between the sources it uses for energy. This leads to improved metabolic flexibility, which is linked with better cardiometabolic health. In other words, this means lower risk of cardiovascular disease, insulin resistance and type 2 diabetes.

My colleagues and I previously ran a study to demonstrate the effects of a fast on the body. We observed that following a day of both total fasting or severe calorie restriction (eating around only 25% of each person’s daily calorie requirements), the body was better at clearing and burning the fat of a full English breakfast the next day. Fasting shifted the body from using carbs to using fat. This effect carried on both during the fast and the next day.

Our research has also compared the effects of intermittent fasting to a calorie-matched or calorie-restricted diet. Both groups followed the diet until they lost 5% of their body weight.

Despite both groups losing the same 5% of body weight, and at the same rate, the intermittent fasting group had greater improvements in their metabolic handling, similar to what we saw in the previous trial.

Other researchers who have compared the effects of the 5:2 variant of the intermittent fasting diet to a calorie-matched, calorie-restricted diet have also found fasting is beneficial for metabolic health.

Metabolic health benefits

But why exactly is intermittent fasting so beneficial for metabolic health? This is a question I sought to answer in my latest study.

For people who follow the 5:2 intermittent fasting diet, typical fasting days are, by their nature, very low in calories – equating to only a few hundred calories per day. Because people are consuming so few calories on fasting days, it also means they’re consuming very few carbohydrates. Given the postprandial state is governed by carbohydrate availability, this begged the question as to whether it’s the calorie restriction or the carbohydrate restriction that’s creating the metabolic effect when intermittent fasting.

We recruited 12 overweight and obese participants. Participants were first given a very low-carb diet one day. Another day, they were given a severely calorie-restricted diet (around 75% fewer calories than they’d normally eat). After each fasting day, we gave them a high-fat, high-sugar meal (similar to an English breakfast) to see how easily their bodies burned fat.

What we found was that the shift to fat burning and improved fat handling of the high-calorie meal were near identical following both the traditional calorie-restricted “fast” day and the low-carb day. In other words, restricting carbs can elicit the same favourable metabolic effects as fasting.

It will be important now for more studies to be conducted using a larger cohort of participants to confirm these findings.

Such findings may help us address some of the practical problems we face with intermittent fasting and traditional low-carb diets.

For intermittent fasting diets, severe calorie restriction on fasting days can increase the risk of nutritional deficiencies if not careful. It can similarly be a trigger for disordered eating.

Strict carb restriction can also be challenging to adhere to long-term, and may lead to an unhealthy fear of carbs.

The other limitation of both intermittent fasting and continuous carb restriction is that weight loss is a likely outcome. Hence these approaches are not universally beneficial for those who need to improve their health without losing weight or those looking to maintain their weight.

We are now testing the feasibility of an intermittent carb restriction diet, or a low-carb 5:2. So instead of restricting calories two days a week, you would restrict the number of carbs you consume twice a week. If this is proven to be beneficial, it would offer the benefits of fasting without restricting calories on “fast” days.

Adam Collins, Associate Professor of Nutrition, University of Surrey

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Categories : Cancer GastrointestinalTags :

Low-carb Diet’s Colorectal Cancer Risk is Mediated by the Gut Microbiome

On By ModernMedia
Gut Microbiome. Credit Darryl Leja National Human Genome Research Institute National Institutes Of Health

Researchers from the University of Toronto have shown how a low-carbohydrate diet can worsen the DNA-damaging effects of some gut microbes to cause colorectal cancer.

The study, published in the journal Nature Microbiology, compared the effects of three different diets: normal, low-carb, or Western-style with high fat and high sugar, each in combination with specific gut bacteria on colorectal cancer development in mice.

They found that a unique strain of E. coli bacteria, when paired with a diet low in carbs and soluble fibre, drives the growth of polyps in the colon, which can be a precursor to cancer.

“Colorectal cancer has always been thought of as being caused by a number of different factors including diet, gut microbiome, environment and genetics,” says senior author Alberto Martin, a professor of immunology at U of T’.

“Our question was, does diet influence the ability of specific bacteria to cause cancer?”

To answer this question, the researchers, led by postdoctoral fellow Bhupesh Thakur, examined mice that were colonized with one of three bacterial species that had been previously linked to colorectal cancer and fed either a normal, low-carb or Western-style diet.

Only one combination, a low-carb diet paired with a strain of E. coli that produces the DNA-damaging compound colibactin, led to the development of colorectal cancer.

The researchers found that a diet deficient in fibre increased inflammation in the gut and altered the community of microbes that typically reside there, creating an environment that allowed the colibactin-producing E. coli to thrive.

They also showed that the mice fed a low-carb diet had a thinner layer of mucus separating the gut microbes from the colon epithelial cells. The mucus layer acts as a protective shield between the bacteria in the gut and the cells underneath. With a weakened barrier, more colibactin could reach the colon cells to cause genetic damage and drive tumour growth. These effects were especially strong in mice with genetic mutations in the mismatch repair pathway that hindered their ability to fix damaged DNA.

While both Thakur and Martin emphasize the need to confirm these findings in humans, they are also excited about the numerous ways in which their research can be applied to prevent cancer.

Defects in DNA mismatch repair are frequently found in colorectal cancer, which is the fourth most commonly diagnosed cancer in Canada. An estimated 15 per cent of these tumours having mutations in mismatch repair genes. Mutations in these genes also underlie Lynch syndrome, a genetic condition that significantly increases a person’s risk of developing certain cancers, including colorectal cancer.

“Can we identify which Lynch syndrome patients harbour these colibactin-producing microbes?” asks Martin. He notes that for these individuals, their findings suggest that avoiding a low-carb diet or taking a specific antibiotic treatment to get rid of the colibactin-producing bacteria could help reduce their risk of colorectal cancer.

Martin points out that a strain of E. coli called Nissle, which is commonly found in probiotics, also produces colibactin. Ongoing work in his lab is exploring whether long-term use of this probiotic is safe for people with Lynch syndrome or those who are on a low-carb diet.

Thakur is keen to follow up on an interesting result from their study showing that the addition of soluble fibre to the low-carb diet led to lower levels of the cancer-causing E. coli, less DNA damage and fewer tumours.

“We supplemented fibre and saw that it reduced the effects of the low-carb diet,” he says. “Now we are trying to find out which fibre sources are more beneficial, and which are less beneficial.”

To do this, Thakur and Martin are teaming up with Heather Armstrong, a researcher at the University of Alberta, to test whether supplementation with a soluble fibre called inulin can reduce colibactin-producing E. coli and improve gut health in high-risk individuals, like people with inflammatory bowel disease.

 “Our study highlights the potential dangers associated with long-term use of a low-carb, low-fibre diet, which is a common weight-reducing diet,” says Martin.

“More work is needed but we hope that it at least raises awareness.”

Source: University of Toronto

Categories : Metabolic DisordersTags :

A Simple Tweak to Breakfast may Help Glycaemic Control in T2D

On By ModernMedia
Photo by Towfiqu Barbhuiya on Unsplash

Research suggests that a simple tweak to the breakfast menu might help people living with Type 2 diabetes (T2D) better control their blood sugar levels. The study, published in the American Journal of Clinical Nutrition, confirms that switching from a traditional Western-style low-fat breakfast, like oatmeal, toast and fruit, to a low-carb meal higher in protein and fat, like eggs with bacon or cheese, can help people with T2D better manage their blood sugar for most of the day.

Dr Barbara Oliveira conducts research with Dr Jonathan Little’s Exercise, Metabolism and Inflammation Lab in UBCO’s Faculty of Health and Social Development. “We’re not talking about a complete diet overhaul,” says Dr Oliveira. “One of many complications for people living with T2D is rapid or large increases in blood glucose levels after a meal. Our research indicates a low-carbohydrate meal, first thing in the morning, seems to help control blood sugar throughout the day.”

Controlling glucose levels is critical for reducing the complications of T2D including inflammation and cardiovascular disease – the major cause of morbidity in patients with T2D.

“Treatment strategies that can help lower post-meal glucose swings and rapid changes in glucose are crucial to managing this condition,” she adds. “We’ve determined that if the first meal of the day is low-carb and higher in protein and fat we can limit hyperglycaemic swings.”

Low-carb diets have become trendy in recent years and have been recognised as a dietary strategy to improve glucose control, Dr Oliveira explains. However, similar to all diets, it’s tough to follow, especially long term. Instead of asking patients to commit to every meal being low-carb, she and Dr Little examined the idea of making just the first meal of the day low-carb to see how that impacts diet adherence, and more importantly, blood glucose levels.

Their 12-week study had 121 participants split into two groups. One was advised to eat from a selection of low-carb breakfasts containing approximate amounts of 8g of carbohydrate, 25g of protein and 37g of fat while the other was advised to eat from a selection of low-fat higher-carb options containing about 56g of carbohydrates, 20g of protein and 15g of fat. All the breakfast options in both groups provided 450 calories.

Participants had a variety of breakfast choices and were required to upload a photo of their meal, which was reviewed by a study dietitian to confirm compliance.

All participants were provided with a continuous glucose monitoring device they wore throughout the study and A1c blood tests were done, before and after the 12 weeks. They also measured their weight and waist circumference at the beginning and end of the trial. As the study continued they reported feelings of satiety, energy and activity levels.

Dr Oliveira notes while there were no significant differences between the low-carb and other group for weight, body mass index or waist circumference, the low-carb group did see a reduction in blood sugar levels and some were able to reduce their glucose-lowering medication. The upward and downward swings in blood glucose levels, known as glycaemic variability, with the low-carb group was also significantly lower, suggesting the benefits of a low-carbohydrate breakfast for stabilizing blood sugars throughout the day.

One additional interesting finding was that people who had the low-carb breakfast self-reported lower calorie and carbohydrate intake at lunch and during the remainder of the day. This could suggest that a breakfast rich in fat and protein, while lower in carbs, can impact daily eating habits.

“Having fewer carbs for breakfast not only aligns better with how people with T2D handle glucose throughout the day, but it also has incredible potential for people with T2D who struggle with their glucose levels in the morning,” she adds. “By making a small adjustment to the carb content of a single meal rather than the entire diet, we have the potential to increase adherence significantly while still obtaining significant benefits.”

Source: University of British Columbia

Categories : Ageing Diet and NutritionTags :

Can Low-carbohydrate or Low-fat Diets Extend Lifespan?

On By ModernMedia

Better diets are needed to address the macronutritional needs of an ageing population. Short-term clinical trials have demonstrated the health benefits of low-carbohydrate diets (LCDs) and low-fat diets (LFDs) for weight loss and heart protection. Now a study published in the Journal of Internal Medicine looks at the effects of these diets on mortality in middle-aged and older adults.

In the study of 371 159 individuals aged 50 to 71 years, 165 698 deaths occurred over a median follow-up of 23.5 years.

A healthy LFD – characterised by low intake of saturated fat and high intakes of plant protein and high-quality carbohydrates – was related to fewer deaths from all causes, from cardiovascular diseases, and from cancers. In contrast, an overall LCD and an unhealthy LCD were associated with significantly higher total, cardiovascular, and cancer mortality rates. A healthy LCD was associated with slightly lower death rates.

“Our results support the importance of maintaining a healthy LFD with less saturated fat in preventing all-cause and cause-specific mortality among middle-aged and older people,” the authors wrote.

Source: Wiley