Struggling with excess weight can be incredibly emotionally and physically taxing; leading to loss of confidence and increasing risk of a wide range of undesirable health outcomes. Fortunately, there’s a lot we can do about it with diet.
One of the many benefits I’ve experienced from adopting a vegan diet is the amount of weight I’ve effortlessly lost. Choosing only healthy, minimally processed plant foods, I really just eat as much as I like, and I don’t stress over self-restriction; good thing because I LOVE food. I also find I’m much more active too, since my energy levels are unbelievably high these days.
Does science show that vegans are more slender?
Weight loss on a vegan diet is not just my personal anecdote; over twenty studies have found vegans (those following an entirely plant based diet) to have lower BMIs and low body fat percentages than other dietary groups.1 In fact, in the Adventist Health Study 2 (a study of 96,000 people) including large numbers of vegans, vegetarians, pescatarians and meat eaters, found that vegans were the ONLY group to fall within the normal BMI bracket.
It’s not only studies looking at large numbers of existing plant eaters who find this the best way for optimising weight; when this same diet has been used as an intervention to observe weight loss, results have also been thoroughly impressive. The BROAD study was a 12 month intervention where 65 people with elevated BMI or poor lipid readings were split into two groups; one to receive “regular care“, and the other to follow an eat as much as you like whole food plant based diet with B12 supplementation. After twelve months the whole food plant based group had lost an average of 4.2 BMI points (That’s HUGE!) without any mandated exercise or restrictions on the amount of food they were allowed to eat. The researchers concluded that to the best of their knowledge, no other intervention that didn’t require calorie control or mandate exercise had achieved greater weight loss at 6 or 12 months.
So what exactly that makes a vegan diet a “magic pill” when it comes to reaching and maintaining a healthy body weight? Whilst even more mechanisms exist, some of the most important are the following:
1.Reduced calorie density
People tend to eat around the same weight of food during meals, so when the foods they eat are (low calorie density) low in calories proportional to their weight, they end up consuming less calories unintentionally, whilst still feeling full and satisfied as the foods still register with the stomach as a large volume. Plant foods that are minimally processed are high in water content and fibre, making them lower calorie density.
Fruits, vegetables and leafy greens are the super stars when it comes to this, so if you’re trying to lose weight then stuff your plate full of these foods! Beans and wholegrains are also lower calorie density than animal foods and really must be included in a healthy plant based diet. This is a way to lose weight whilst feeling full and satisfied!
If you’re already on a plant based diet and struggling with reducing your weight, here are a food foods to look out for:
Foods that are very high in calorie density on a plant based diet include foods with minimum water (such as bread, dried fruit, nuts). Oil packs a huge amount of hidden calories in food; each tablespoon provides around 120 calories. In addition to hefty use of salt, I’d say this is one of the top reasons why you’ll typically notice a natural weight reduction when you increase the amount of food you eat at home.
2. Improved gut microbiota symbiosis
The gut microbiome is such as fascinating topic when it comes to influencing so many health outcomes in the body. Whilst many people know that the health of your microbiota can strongly impact digestive symptoms and even mental health symptoms, fewer people realise what impact it exerts on weight.
The gut microbiome can not only influence energy balance, but influence satiety and gut inflammation. Incredibly, the Bacteroidetes taxa has been associated with reduced obesity compared to Firmicutes. One randomized cross over trial showed a 20% increase in Firmicutes bacteria to associate with around 150 greater kilocalories absorbed, compared to a 20% increase in Bacteroidetes associating with around 150 fewer kilocalories absorbed2.
Interestingly, when weight loss is achieved through reducing total calories (as typically happens effortlessly with the adoption of a whole food plant based diet), bacterial gut populations shift from Firmicutes to Bacteroidetes. It’s as if your body realises you’re trying to lose weight, and starts to give you a helping hand once you make that initial change!
Another really cool thing happens when you load your plate with whole plant foods which are naturally high in fibre (you won’t find any fibre in animal foods); when undigestible fibres are fermented in the colon, short chain fatty acids are produced. Short chain fatty acid production leads to the release of peptide YY (a hormone that hunger and consequently food intake), in addition to glucagon-like peptide (a hormone that delays gastric emptying).
- Look for your wholegrains and beans for great sources of that undigestible fibre.
- The NUMBER 1 determinant of a healthy diverse microbiome, as stated by expert Rob Knight from the American Gut Project, is the diversity of plant foods contained in the diet; that means try and get as much variety and colour on your plate!
3. Increased insulin sensitivity
High-fibre, plant-based diets (composed primarily of healthy unrefined carbohydrates and low in saturated fats) have been shown to be incredibly effective in increasing insulin sensitivity and treating Type 2 diabetes 3.
Improving insulin sensitivity may directly impact body weight, improved insulin sensitivity leads to better glucose handling and consequentially increased energy expenditure from carbohydrate ingestion4. This may partially explain why a number of interventions using similar calorie intakes for nonvegetarian and plant-based participants have led to greater reductions in fat mass by those in the plant-based group.
Pro-tip: Improving insulin sensitivity requires reducing saturated fat intake. Whilst this is achieved fairly easily through adopting an whole food plant based diet, one sneaky “health food” is laden with saturated fat- coconut. Whilst coconut is DELICIOUS, it is extremely high in saturated fat, and making it a regular part of the diet may be problematic for weight loss goals. Enjoy the occasional fresh coconut, but minimise use of all cooking oils (including coconut!) if weight loss is a goal.
Together, these mechanisms lead to increased satiation and increased energy expenditure, leading to natural, effortless weight loss.
It’s important to note that this is only true of whole food plant-based diets; a chips and Coca Cola vegan diet is unlikely to result in weight loss, and certainly won’t lead to favourable health outcomes. If you’d like any help with your weight loss journey and a personalised programme put together, I would love to work with you!
- Mangels R, Messina V. The Dietitan’s Guide to Vegetarian Diets: Issues and Applications. 3rd ed. Sudbury, MA: Jones and Bartlett Learning; 2010.
- Jumpertz R, Le DS, Turnbaugh PJ, et al. Energy-balance studies reveal associations between gut microbes, caloric load, and nutrient absorption in humans. Am J Clin Nutr. 2011;94(1):58-65. doi:10.3945/ajcn.110.010132
- Tonstad S, Butler T, Yan R, Fraser GE. Type of vegetarian diet, body weight, and prevalence of type 2 diabetes. Diabetes Care. 2009;32(5):791-796. doi:10.2337/dc08-1886
- Ravussin E, Acheson KJ, Vernet O, Danforth E, Jéquier E. Evidence that insulin resistance is responsible for the decreased thermic effect of glucose in human obesity. J Clin Invest. 1985;76(3):1268-1273. doi:10.1172/JCI112083