Most people who switch to a plant-based diet tend to lose weight. Many manage to shed pounds without even trying or keeping track of their caloric intake.
This isn’t just anecdotical, by the way. Vegans have the lowest BMI of any dietary group.
How does this happen?
A lot of benefits of plant-based eating, weight loss very much included, derive from two characteristics of this diet. Namely, plant-based eating tends to have low-calorie density and high-nutrient density.
These facilitate dietary displacement which is a great strategy for weight loss. The basic idea is that if you eat enough nutritious foods each day, you’ll be left with little room for highly-processed foods with no nutritional value.
Low-calorie density
Weight loss ultimately comes down to a matter of energy balance. There are many factors affecting the calories in and calories out equation, but in the end, if you eat fewer calories than you burn, you will lose weight.
There are many variables that determine how satiating a given food is, but three key components are (in order of importance):
- Water content;
- Fiber content;
- Nutrients.
Plant-based diets are full of water-rich foods. Since water doesn’t have any calories in it, you end up eating a lot of food (volume and weight-wise) for relatively few calories.
Plant-based diets are also full of fiber-rich foods. Fiber enables you to feel full for longer because high-fiber foods take longer to digest. (Among the many other benefits of fiber, including lowering your LDL cholesterol by hindering the reabsorption of bile salts.)
The average person would be hard-pressed to eat 2,000 calories/day solely from fruits and vegetables high in water and fiber content. On the other hand, they could eat 2,000 calories of cookies in 20 minutes, and be hungry two hours later.
Once you start incorporating plant-based foods with low caloric density into your diet, you’ll naturally end up eating fewer calories because you won’t be as hungry and there is only so much space in your stomach.
Once your stomach begins stretching, nerve receptors within it will send signals to your brain via the vagus nerve that you had enough food.
Vagal fibers in the stomach respond mainly to volume (i.e., stretch and tension), while those in the intestine respond mainly to nutrient content.
Dr. Timothy Moran
You might have heard that fat and protein are more satiating than carbohydrates. That’s true, but calorie per calorie, the volume of the food matters far more.
Compare these two meals.
MEAL A (580 cal)
- 100g / 3.5 oz of White Bread (266 cal)
- 2.5 tbsp of Olive Oil (300 cal)
- 1 tbsp of Balsamic Vinegar (14 cal)
MEAL B (548 cal)
- 400g / 14.1 oz of Broccoli (140 calories)
- 300g / 10.5 oz of Sweet Potatoes (258 cal)
- 500g / 17.6 oz of Watermelon (150 calories)
Though meal B is actually lower in calories, it offers a huge amount of food.
Many people would struggle to finish such a meal in one sitting. This meal has 5.6 cups of broccoli, 1.5 cups of sweet potatoes, and 3.3 cups of watermelon. That’s over 10 cups or 2.6 lb of food.
For reference, the average stomach has a volume of about a liter (~ 4 cups). It can stretch to accommodate more food (in the 2-4 liter range, depending on the person), but you will start to experience discomfort as you stretch it further and further.
Meanwhile, meal A is a snack or an appetizer (it’s just some bread dipped in oil and vinegar). Most people would still be hungry after its consumption.
This example stresses how you can really stretch out your calories when you eat calorically dilute foods such as most fruits and vegetables. That’s far more important for satiety than their macronutrient make up (fats, proteins, and carbs). After all meal A is mostly fat, which is satiating, and meal B is mostly carbs, which is not.
The caloric density of food, defined as the number of calories per pound, is a key factor in how satiated you’re going to be.
The following table shows the typical, approximate caloric density of some main types of foods.
| Food Type | Calories per lb |
| Non-starchy vegetables | 100 cal |
| Mushrooms | 100 cal |
| Fruit | 200 – 300 cal |
| Potatoes / Starchy vegetables | 400 cal |
| Whole grains | 500 cal |
| Beans and legumes | 600 cal |
| Avocados | 700 cal |
| Ice Cream | 1,200 cal |
| Bread | 1,200 – 1,400 cal |
| Cheese | 1,600 cal |
| Sugar | 1,800 cal |
| Milk chocolate bar | 2,400 cal |
| Nuts and seeds | 2,800 cal |
| Butter | 3,300 cal |
| Oils | 4,000 cal |
If your diet is mostly comprised of foods with a density below 600 calories per pound, you’re likely to eat several pounds of satiating food, rarely be hungry, and still keep your calories in check.
This is why a plant-based diet that includes plenty of fruits and vegetables will be naturally and effortlessly less caloric than virtually any other type of diet.
High-nutrient density
The second secret weapon of plant-based diets is that they are full of micronutrients. That is vitamins, minerals, antioxidants, and phytonutrients (beneficial substances found only in plants).
Compare the vitamin and mineral content of the two meals outlined above (bread and oil on the left, broccoli, sweet potatoes, and watermelon on the right).
As you can see, it’s not just that meal B is significantly more satiating. It’s also more nutritious.
Plant-based diets not only tend to make you lose weight without starving yourself, but they also feed your body with the micronutrients it needs (exception made for vitamin B12 that you must supplement).
Note, that we didn’t intentionally pick those specific vegetables and fruit. We went with a random selection of calorically dilute foods. It would be possible to select foods with more complementary micronutrient profiles and make the contrast in the image above between the two meals even more dramatic.
You can still make poor choices as a vegan
Have you ever heard the term “empty calories”? What empty calories refer to is foods (often processed foods) that are high in calories but provide very little micronutrients (or protein). Examples include cookies, donuts, ice cream, etc.
Being vegan or plant-based is not a vaccine against such foods, unfortunately.
Meal A, which wasn’t the worst choice ever but it’s not great either, is plant-based after all. So you can easily make bad choices even if you are vegan and don’t eat animal products.
However, since you have cut out meat (which tends to be fairly caloric and high in saturated fat and cholesterol), cheese (which is even more caloric), and a lot of the processed foods that include dairy and/or eggs, you are more likely to opt for a diet that is rich in fruit and vegetables.
Again, plant-based processed junk does exist, and even Oreos are technically vegan. So it’s up to you to leverage those two secret weapons of plant-based diets and make them work for you by aiming for foods that are less calorically dense and more nutritionally rich.
If the bulk of your food comes from such foods, it’s okay to incorporate more calorie-dense foods in moderation. Having an ounce (28 g) of nuts per day, as caloric as they are, will not affect your results. Eating them by the handful while you watch TV, will likely derail you (unless your goal is to gain weight, in which case nuts are an excellent choice).
A whole-foods, plant-based diet is essentially the antithesis of an empty calorie diet. If you orient your diet towards it, the occasional meat substitute processed food or more calorically dense food such as dairy-free ice cream, is unlikely to put you in a major caloric surplus and cause you to gain significant weight.
As long as you take a mostly whole-foods, plant-based approach to your diet, you’ll be on your way to improving your health and body composition.
Now that you know about the secret weapons, all you have to do is use them to your advantage.
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