Low-fat vegan diet better than Med diet for weight loss and inflammation, new research flags

12 Aug 2024 --- A 36-week crossover trial conducted by the Physicians Committee for Responsible Medicine (PCRM) found that following a low-fat vegan diet reduces weight and harmful advanced glycation end-products (AGEs) inflammatory dietary compounds. The decrease in AGEs was mainly attributed to excluding meat (41%), the reduction in added fat consumption (27%) and the increased absence of dairy products (14%).

“The study helps bust the myth that a Mediterranean diet is best for weight loss. Choosing a low-fat vegan diet that avoids the dairy and oil so common in the Mediterranean diet helps reduce intake of harmful advanced glycation end-products leading to significant weight loss,” says Dr. Hana Kahleova, Ph.D., director of clinical research at the PCRM and lead author of the study.

The study’s findings, published in Frontiers in Nutrition, observed that the reduction in AGEs on the vegan diet was associated with an average weight loss of 6 kg compared with no change on the Mediterranean diet.

AGEs can contribute to the pathogenesis of insulin resistance and increased body weight by directly modifying signaling molecules such as insulin itself and affinity for the insulin receptor. 

It also contributes to the development of insulin resistance through the modification of the three arginine residues in the adenosine monophosphate-activated protein (AMP) binding site of AMP kinases, decreasing their interference with the activation of downstream proteins involved in cell insulin signaling.

Regulating AGEs

The new research is a secondary analysis of a previous study conducted by the committee comparing a low-fat vegan diet to a Mediterranean diet. Sixty-two overweight adults were randomly assigned a Mediterranean or low-fat vegan diet for 16 weeks, separated by a four-week washout. Three-day diet records were analyzed using the Nutrition Data System for Research software, and dietary AGEs were estimated using an established database. Statistical approaches appropriate for crossover trials were implemented.

 “Our research shows that you can use the power of your plate to lose weight with a low-fat vegan diet rich in fruits, vegetables, grains and beans and low in AGEs. It’s a simple and delicious way to maintain a healthy weight and fight chronic disease,” says Kahleova. 

Animal products are mainly higher in AGEs than plant foods. Cooking with high heat under dry conditions, such as grilling, causes a significant formation of AGEs, especially in animal-derived foods, which are also rich in fats.

High amounts of AGEs circulating in the body can contribute to insulin resistance, which leads to weight gain. AGEs are also linked to inflammation and oxidative stress, which contribute to chronic diseases like heart disease and type 2 diabetes.

Roughly 70% of US adults are overweight and the extra weight is often associated with an increased cardiometabolic risk and partly due to accelerated production of AGEs. AGEs are a large heterogeneous group of compounds formed during a non-enzymatic reaction of the carbonyl groups of sugars with free amino groups in protein.A low-fat vegan diet reduces AGEs and weight.

Several randomized interventional trials have shown that dietary AGE restriction ameliorates insulin resistance in obese people with metabolic syndrome.

In addition, the findings of a recent twin study posited that following a vegan diet for eight weeks is associated with a decrease in biological age estimations based on DNA methylation levels, and were met with several cautionary reactions from other experts in the field.

Keeping dietary records

Neither group had a calorie limit. Participants then returned to their baseline diets for a four-week washout before switching to the opposite group for an additional 16 weeks. Dietary AGEs were calculated based on self-reported dietary intake records. AGE scores were assigned to each food item.

Previous studies observed that the Mediterranean diet reduces dietary and serum AGE in elderly adults compared with a Western diet rich in saturated fat.

 The current study’s population was more health conscious at baseline, consuming only 10% energy than saturated fat than the experimental Western diet, which contained 22% energy in the form of saturated fat. The researchers say this may explain why there was no reduction in dietary AGEs observed on the Mediterranean diet. 

The reduction in dietary AGEs from a low-fat vegan diet has previously been reported in overweight adults and postmenopausal women.

 The current study compares the effects of a Mediterranean diet to a low-fat vegan diet and shows a beneficial effect of a low-fat vegan diet. The study shows which dietary changes contributed most to the reduction of dietary AGEs on a low-fat vegan diet, mainly excluding meat consumption, reducing fat and avoiding dairy products.    

According to the researchers, the study has several strengths, including a crossover design that allowed them to directly compare the effects of a Mediterranean diet and a low-fat vegan diet. The 84% retention (high) suggests that both diets are acceptable. The duration of the study was another favorable variable because it allowed enough time for metabolic adaptation.  

Meanwhile, the US News and World Report ranked the Mediterranean diet as the best out of 30 diets, followed by the DASH (Dietary Approaches to Stop Hypertension) and MIND diet — a combination of the Mediterranean and DASH diets, in its annual evaluation of best diets, 

In addition, new research suggests that the Mediterranean diet may boost mental health and help relieve stress. This adds a new element to a diet that has been shown to have cardiometabolic and weight management benefits, along with being able to reduce the risk of developing bowel cancer and dementia. Additionally, the study’s authors say it could represent a new option for the relief from anxiety and stress-related symptoms.

By Inga de Jong