Trying a diet without adding fats or animal products can be a great way to start your weight loss efforts. In a study published in November 2020 in JAMA network openEating this way helped overweight and obese people lose an average of 5.9 pounds (about 13 pounds) over 16 weeks.
The study randomly assigned 244 overweight and obese individuals to start a low-fat vegan diet or to join a control group that made no dietary changes. People on the vegan diet attended weekly classes with demonstrations of cooking and nutritional support, and they were encouraged to consume vegetables, fruits, whole grains and legumes while avoiding the addition of fats and animal products.
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While participants in both groups consumed fewer calories during the 16-week trial than they did before the start of the experiment, people on the vegan diet managed to reduce an average of 355 calories per day more than people in the control group.
It is likely that people lost more weight partly because they consumed fewer high-fat, high-calorie foods, and partly because they replaced animal products with healthier plant-based foods, says study lead author Hana Kahleova, MD, PhD , director of clinical research at the Committee of Physicians for Responsible Medicine in Washington, DC.
“Eliminating foods high in fat and cholesterol is one part, and the other is replacing these foods with plant foods that are rich in fiber and antioxidants,” says Dr. Kahleova. “Both play an important role in improving cardiometabolic health.”
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So-called cardiometabolic risk factors, such as blood sugar levels, cholesterol levels, and blood pressure, can indicate your risk of having events such as 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 accelerated their metabolism after eating; and they reduced the amount of fat that accumulates inside the cells.
“Our study has shown that this diet addresses the underlying mechanisms behind obesity, diabetes and cardiovascular disease, all at the same time,” says Kahleova.
A limitation of the study is that participants prepared their meals and used food diaries to find what they consumed, both of which may not be reliable indicators of how closely people followed a vegan low-fat diet. It is also not clear from the study how this type of diet can affect long-term weight loss.
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Previous studies show the health benefits of a 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 such as 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 reduce the risk of cancer by 18 percent, according to AAND guidelines.
“A low-fat vegan diet can be beneficial in promoting health and preventing disease whether 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 and Delicious Vegetarian Recipeswith
“It can be effective for weight loss even among those who have only a few pounds to lose or are only slightly overweight,” says Sheth, who was not included in the current study.
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And a previous 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 – within the range of 18 to 24.9 which is considered a normal or healthy weight. Groups with other types of diets all had average BMIs within the overweight range of 25 to 29.9: Vegetarians who ate milk and eggs had an average BMI of 25.7; vegetarians who ate fish had an average BMI of 26.3; and non-vegetarians had an average BMI of 28.8.
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How to switch to a plant-based diet
If the idea of going cold turkey and removing all meat, fish, cheese and eggs from your diet sounds impossible, it makes sense to start with less drastic changes, say health experts.
“I would expect very few patients to be willing to switch from a comprehensive diet to a vegan diet,” says J. David Spence, MD, director of the Research Center for Stroke Prevention and Atherosclerosis at the Robarts Research Institute in London , Ontario, Canada.
Instead, it may be easier to focus on following a Mediterranean diet that incorporates many aspects of a plant-based diet: high consumption of fruits and vegetables, whole grains, legumes, and nuts, says Dr. Spence, who was not included in the study This type of diet also emphasizes lean fish and protein rather than red and processed meat.
Eating this way can help build healthier habits over time even if people do not become completely vegan, says Samantha Heller, RDN, a nutritionist at New York University Langone Medical Center in New York City.
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“In my experience, when patients switch to eating less processed foods, their cravings for food tend to diminish over time, so they are less likely to consume leftovers and fast foods, and sweets, says Heller, who was not involved in the study.
If you want to become vegan, or try to eliminate some meat from your diet, it can work better and be more sustainable over time if you start slowly, Heller advises. This could mean making meatless or cheese-free meals only a few days a week, or replacing the breakfast sandwich with bacon, eggs and cheese with a breakfast burrito mixed with tofu.
Instead of focusing on what your diet is called or if it is strictly vegan, you should focus on consuming fruits, vegetables, whole grains and beans, and including all the colors of the rainbow from fresh, whole foods, Kahleova says.
For inspiration, check out some recipes from the Physicians Committee for Responsible Medication.
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