Plant-Based Diets vs. Animal-Based Diets

Some people feel that a low-fat, plant-based diet is the healthiest. Others think a low-carb, animal-based diet takes the cake. But a new study suggests they both offer different benefits and drawbacks.

This new study compared the effects of animal-based and plant-based diets on calorie intake, insulin and glucose levels and weight loss.

Because there is debate over whether people should limit carbohydrate intake or dietary fat intake, this study aimed to shed some light on the effects of diets that emphasize each of these approaches.

“High-fat foods have been thought to result in excess calorie intake because they have many calories per bite," said lead study author Dr. Kevin Hall, of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), in a press release. "Alternatively, high-carb foods can cause large swings in blood glucose and insulin that may increase hunger and lead to overeating."

To investigate the two diets, NIDDK researchers observed 20 men and women who lived at a National Institutes of Health facility for four weeks. The study group received either a low-fat, plant-based diet or a low-carb, animal based diet for two weeks. Then, each person switched to the alternate diet. The participants received three meals per day and snacks. They could eat as much as they wanted.

Participants eating the low-fat, plant-based diet ate 550 to 700 calories fewer than those eating the animal-based diet each day, this study found. While participants lost weight when eating both diets, the plant-based diet led to a significant loss of body fat.

Participants eating the low-carb, animal-based diet had lower blood glucose and insulin levels than those eating the plant-based diet. Having elevated levels of these hormones is tied to health problems like diabetes.

“Interestingly, our findings suggest benefits to both diets, at least in the short-term," Dr. Hall said. "While the low-fat, plant-based diet helps curb appetite, the animal-based, low-carb diet resulted in lower and more steady insulin and glucose levels. We don’t yet know if these differences would be sustained over the long term.”

Not all diets are healthy for all situations. Talk to your health care provider before making any major changes to your diet.

This study was published in Nature Medicine.

The NIDDK Intramural Research Program and federal grants funded this research. Study authors received speaking fees and research funding from nutrition-focused companies. The researchers declared no other potential conflicts of interest.