Plant-Based High-Carb Diet Does Not Lead To Weight Gain, NIH Study Finds

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A new study from the U.S. National Institutes of Health (NIH) finds that contrary to popular belief, high-carb and low-fat plant-based diets do not necessarily lead to any weight gain. While the study was only conducted on a small-scale, the findings do suggest that factors resulting in overeating and weight gain are far more complex than the amount carbs or fat we consume in our diet. 

The NIH study published in the journal Nature Medicine compares low-fat plant-based diets with low-carb animal-based diets. While it only involved a small number of 20 adult participants, it was highly controlled and investigated how the variation in diets affected calorie intake, hormone levels and body weight with an aim to further our understanding of how carbohydrates and fats could impact health. 

“Our study was designed to determine whether high-carb or high-fat diets result in greater calorie intake,” explained lead author Dr. Kevin Hall. 

For four weeks, the participants were housed at an NIH clinical centre and were provided with either the plant-based, high-carb diet or the low-carb, animal-based diet for two weeks, followed by the alternate diet for the next two weeks. Both diets were designed to be minimally processed, had similar levels of vegetables and participants were able to eat as much as they wanted of what they were given. 

What the researchers found was that those on a low-fat, plant-based, high-carb diet tended to eat fewer calories than the low-carb animal-based diet, and actually led to a significant loss of body fat, contrary to popular belief that diets that are high in carbohydrates lead to weight gain. 

“Despite eating food with an abundance of high glycemic carbohydrates that resulted in pronounced swings in blood glucose and insulin, people eating the plant-based, low-fat diet showed a significant reduction in calorie intake and loss of body fat, which challenges the idea that high-carb diets per se lead people to overeat,” explained Hall. 

But those who ate high-fat, low-carb diets did not necessarily gain any weight either. “On the other hand, the animal-based, low-carb diet did not result in weight gain despite being high in fat,” Hall continued. 

The researchers believe that the study confirms that weight gain and overeating is far more complicated than previously thought, and goes beyond the simplistic view of the amount of carbohydrates or fats that one consumes

In his previous 2019 research, a study led by Hall overturned the conventional belief that overconsumption of fats and carbohydrates leads to obesity, and instead suggested that “ultra-processed foods” or UPFs – instant, long shelf-life convenient foods that have undergone significant processing – was the bigger culprit.

Read: It isn’t about salt, sugar, fats & carbs. Are ultra-processed foods to blame for obesity? 

Some UPFs are obvious, such as the conventional fare of fast food meals, chicken nuggets and the like. Other types may even be marketed as “healthier” alternatives, such as “lighter” margarines and vitamin-fortified breakfast cereals. 

Dr. Griffin P. Rodgers of the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says that the latest highly controlled study that compares high-carb and low-carb diets deepens our understanding of the complex nature of health, and will enable further research into how our diets can impact health in different ways. 

“To help us achieve good nutrition, rigorous science is critical − and of particular importance now, in light of the Covid-19 pandemic, as we aim to identify strategies to help us stay healthy,” said Rodgers. “This study brings us closer to answering long-sought questions about how what we eat affects our health.”


Lead image courtesy of Getty Images / iStockphoto.

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