Stanford study identifies what influences weight loss the most

Researchers from Stanford University have pinpointed a number of factors that could predict how successful an individual will be at losing weight and keeping it off.

A study from Stanford Medicine, published Dec. 13, 2022, in the peer-reviewed journal Cell Reports Medicine, says some people are better at losing weight on low-fat diets, while others will see better results on low-carb diets.

How well a person adheres to their diet will influence how much weight they lose, as well as the types of bacteria living in their gut, the amount of certain proteins the body makes and how much carbon dioxide a person exhales, the researchers say.

• Tailor the news you receive straight to your inbox by signing up for our newsletters

• Download our app to get breaking news alerts delivered right to you

"Weight loss is enigmatic and complicated, but we can predict from the outset with microbiome and metabolic biomarkers who will lose the most weight and who will keep it off," Michael Snyder, chair of the genetics department at Stanford Medicine and co-senior author of the paper, said in a story published on Jan. 4 by Stanford Medicine.

The study focused on data from a previous yearlong study on weight-loss that involved 609 people, who ate either a low-fat or low-carb diet of mostly high-quality, minimally processed food.

The research also tracked how much participants exercised, how well they followed their diets and their calorie intake.

The study's authors found that simply cutting calories or exercising were not enough to maintain weight loss over a year.

"We found specific microbiome ecologies and amounts of proteins and enzymes at the beginning of the study period — before people started following the diet — that indicated whether they would be successful at losing weight and keeping it off," said Dalia Perelman, a research dietician and co-lead author of the paper.

The researchers also measured the ratio of inhaled oxygen to exhaled carbon dioxide, which they say can determine whether the body prefers to burn carbohydrates or fats as its primary fuel, with a higher ratio meaning the body burns more carbs and a lower ratio meaning it burns more fat.

Those who started their diets with a higher ratio lost more weight on a low-carb diet, the researchers say.

If a person's diet is higher in fat, even though their body prefers to burn carbs, the researchers say it will be harder to burn off those calories.

Ultimately, they say a diet that works for one person may not be suited for someone else.

"There are people who can be eating very few calories but still sustain their weight because of how their bodies metabolize fuels," Perelman said. "It is not for lack of will. It is just how their bodies work."

The study, the researchers say, could lead to personalized weight loss plans.

Without being able to track your own gut microbe strains, the study says people should focus on eating high-quality, unprocessed food that is low in refined flour and sugar.

Low-carb diets should contain monounsaturated fats, such as avocados, and be high in vitamins C, E and K, found in vegetables and nuts, as well as avocados.

Meanwhile, low-fat diets should contain food that is high in fibre, such as whole grains and beans, and low in added sugar.

Both strategies, the researchers say, correlate with weight loss in the first six months of a diet.

"Your mindset should be on what you can include in your diet instead of what you should exclude," Perelman said. "Figure out how to eat more fibre, whether it is from beans, whole grains, nuts or vegetables, instead of thinking you shouldn't eat ice cream. Learn to cook and rely less on processed foods. If you pay attention to the quality of food in your diet, then you can forget about counting calories."

Some limitations of the study include participants generally having a higher level of education, "with good access to many food options."

Some ethnic and racial groups are underrepresented, although the large number of participants in the study helped address this, the researchers say.

The microbiome data also involved a smaller proportion of participants.