Avoiding animal products can rev weight loss and reduce fat accumulation inside cells among overweight and obese people, suggests a recent randomized controlled trial.
Trying a diet without added fats or animal products might be one way to jump-start your weight loss efforts. In a study published in November 2020 in JAMA Network Open, eating this way helped overweight and obese people lose an average of 5.9 kilograms (about 13 pounds) over 16 weeks.
The study randomly assigned 244 overweight and obese individuals to begin a low-fat vegan diet or join a control group that made no dietary changes. People on the vegan diet attended weekly classes with cooking demonstrations and nutrition support, and they were encouraged to consume vegetables, fruits, grains, and legumes while avoiding added fats and animal products.
While participants in both groups consumed fewer calories during the 16-week trial than they did before the experiment started, people on the vegan diet managed to cut back by an average of 355 daily calories more than people in the control group.
It’s likely that people lost more weight in part because they consumed fewer high-fat and high-calorie foods, and in part because they replaced animal products with healthier plant-based meals, says lead study author Hana Kahleova, MD, PhD, director of clinical research at the Physicians Committee for Responsible Medicine in Washington, DC.
“Eliminating foods that are high in fat and cholesterol is one part, and the other one is replacing these foods with plant foods that are rich in fiber and antioxidants,” Dr. Kahleova says. “Both play an important role in improving cardiometabolic health.”
So-called cardiometabolic risk factors like blood sugar levels, cholesterol levels, and blood pressure, can indicate your risk of having events like a heart attack or stroke. People on the vegan diet in the study reduced three key risk factors: They improved insulin sensitivity, or how easily the body converts sugars into energy; they sped up their post-meal metabolism; and they reduced the amount of fat accumulating inside cells.
One limitation of the study is that participants prepared their own meals and used food diaries to track what they consumed, both of which might not be reliable indications of how closely people followed a low-fat vegan diet. It’s also not clear from the study how this type of diet might impact long-term weight loss.
Prior Studies Show Health Benefits of Vegan Diet
The American Academy of Nutrition and Dietetics (AAND) issued guidelines in December 2016 recommending vegan, vegetarian, and other plant-based diets as a way to reduce the risk of obesity, heart disease, and certain cancers.
Following a vegan diet, which excludes meat and fish as well as animal products like eggs and milk, and in some cases honey, can reduce the risk of heart disease by 29 percent, curb the risk of diabetes by 62 percent, and cut the risk of cancer by 18 percent, according to the AAND guidelines.
“A low-fat vegan diet can be helpful in terms of health promotion and disease prevention regardless of if you are overweight, obese, or extremely obese,” says Vandana Sheth, RDN, owner of a private practice in Los Angeles and author of My Indian Table: Quick & Tasty Vegetarian Recipes.
“It may be effective for weight loss even among those who have just a few pounds to lose or are only slightly overweight,” says Sheth, who wasn’t involved in the current study.
And an earlier study published in Diabetes Care suggested that a vegan diet may be more effective for weight loss than other ways of eating. This study examined the body mass index (BMI) and eating habits of more than 22,000 men and more than 38,000 women.
Vegans had the lowest average BMI — 23.6 — well within the range of 18 to 24.9 that’s considered a normal or healthy weight. The groups with other types of diets all had average BMIs within the overweight range from 25 to 29.9: Vegetarians who ate dairy and eggs had an average BMI of 25.7; vegetarians who ate fish had an average BMI of 26.3; and nonvegetarians had an average BMI of 28.8.
How to Transition to a Plant-Based Diet
“I would expect that very few patients would be willing to switch from an omnivore diet to a vegan diet,” says J. David Spence, MD, director of the Stroke Prevention and Atherosclerosis Research Centre at the Robarts Research Institute in London, Ontario, Canada.
Instead, it may be easier to focus on following a Mediterranean diet that includes many aspects of a plant-based diet: high intake of fruits and veggies, whole grains, legumes, and nuts, says Dr. Spence, who wasn’t involved in the study. This type of diet also emphasizes fish and lean protein rather than red and processed meat.
Eating this way can help build healthier habits over time even if people don’t go completely vegan, says Samantha Heller, RDN, a nutritionist at New York University Langone Medical Center in New York City.
“In my experience, when patients switch to eating less highly processed foods, their food cravings tend to diminish over time, so they are less likely to overconsume junk and fast food, and sweets,” says Heller, who wasn’t involved in the study.
If you want to go vegan, or try to eliminate some meat from your diet, it may work best and be more sustainable over time if you start slowly, Heller advises. This might mean making meals without any meat or cheese just a couple days a week, or replacing your go-to bacon, egg, and cheese breakfast sandwich with a tofu scramble breakfast burrito.
Rather than focusing on what your diet is called or whether it’s strictly vegan, you should focus on consuming fruits, vegetables, whole grains, and beans, and incorporating all colors of the rainbow from fresh, whole foods, says Kahleova.
For inspiration, check out a few recipes from the Physicians Committee for Responsible Medicine.