A vegan diet can be great for losing weight because most vegan food (e.g. fruits and vegetables) are high in fiber (which fills you up). Vegan food also tends to be low in calories. However, this does not mean that switching to a vegan diet is guaranteed to result in weight loss as there are vegan foods that are high in calories and low in fiber (e.g. rice and bread). Furthermore, weight loss is dependent not only on calories eaten but also calories burnt (your basal metabolic rate, how much you exercise, etc).
However, there are many people who do not want to lose weight. Many skinny people (especially young men) want to gain weight. Reasons for gaining weight may be cosmetic (skinny men are not attractive) or for health reasons (e.g. anorexia or starvation).
Gaining weight may be the result of more fat in the body or more muscle. More muscle is preferable not only for attractiveness but also for good health. As a man increases his muscle mass, the body automatically burns more calories in order to feed these muscles, which means he does not need to exercise as much. You burn calories simply by existing.
Step 1: Don’t have too much protein
Many skinny young men make the mistake of opting for a high protein diet in order to gain weight. This is a mistake. Numerous studies show that a high protein diet (as opposed to a high-carb diet or even a high-fat diet) blunts your testosterone, which will impair muscle growth.
In the study below, subjects were divided into two groups, one given a high-carb diet and the other given a high-protein diet. Fat intake was equal in both groups. The subjects on a high-carb diet had a significantly higher increase in testosterone levels.
The study below shows that a high-protein diet increases levels of the stress hormone cortisol (high cortisol levels reduce muscle mass).
Step 2: Avoid food high in estrogen
Being on a vegan diet can be great for reducing estrogen levels (and increasing testosterone) because there is a significant amount of estrogen in meat, dairy, and eggs. Most animals that are exploited for food are female, which means natural animal estrogen is present in meat and dairy. Dairy milk especially contains high concentrations of estrone and estradiol, which are cow estrogens. In the study below, men who drank dairy milk regularly suffered from a significant drop in serum testosterone.
That being said, plant food are not entirely free of estrogen. Phytoestrogen (or plant estrogen) are highly concentrated in soy and flax. It is unclear what impact phytoestrogens have on humans. Dr Mark Rosenberg states the following (Could You Be Eating Too Much Estrogen):
[S]ome foods … contain a fair amount of phytoestrogens, or natural, plant estrogen; and synthetic estrogen – man made compounds put into animal feed to stimulate appetite and weight gain. Phytoestrogens do not act the same as synthetic estrogen in the human body. Their hormone stimulating effects are much weaker and can have a self-regulatory effect if natural estrogen blockers … are eaten with them.
Even though it is unclear if phytoestrogens have a significant impact on your body compared to animal estrogen or synthetic estrogen, to be on the safe side, I recommend skinny men avoid or minimize the amount of soy and flax they consume.
Of all meat, grain-fed meat is the most dangerous as animals that eat grain are typically fed soy (although soy is technically a legume), which results phytoestrogen in the animal. The animal is also typically injected with synthetic estrogen to fatten them up quickly. As a result, grain-fed meat has an estrogen triple whammy: plant estrogen, animal estrogen, and synthetic estrogen. Grass-fed animals raised in a traditional and ethical manner would produce meat that contains only animal estrogen.
Step 3: Consume estrogen blockers
Estrogen is hard to avoid in food. They are highest in concentration in soy, flax, grain-fed meat, and dairy milk. That being said, even if a small amount of estrogen gets into your body, food that contains estrogen blockers can be consumed. These lower the amount of estrogen in your body.
Cruciferous vegetables (mainly green vegetables e.g. kale, spinach, brocolli) are excellent estrogen blockers because they contain DIM (3,3′-diindonylmethane), which helps the liver flush out estrogen from your body. A number of low-fructose fruits also lower estrogen levels. These estrogen-lowering fruits include citrus fruits like lemon and oranges, as well as pomegranate.
Step 4: Create your own mass gainer
As I said earlier, most young men make the mistake of chowing down on protein shakes, thinking they will gain weight. This is a mistake. Not only does a high-protein diet blunt testosterone levels but protein fills you up quickly, which means you will consume fewer calories.
If you look at “mass gainers” in bodybuilding stores, the basic formula for these gainers is about 50% to 70% carbs and the remainder is protein. Rather than buy expensive mass gainers, it is better to simply mix oats (a carb) into vegan protein powder. Oats can be purchased from most supermarkets for almost nothing. For better mixability, it is also possible to buy powdered oats or steel cut oats (although these are more expensive).
A benefit of using oats rather than other carbs (such as maltodextrin) is that oats contain saponins, which are a natural steroid that boosts muscle mass. (Quinoa is another good source of saponins.)