You may have heard about chili peppers being recommended as a weight loss supplement, it’s supposed to be helpful because it revs up your metabolism and makes you eat less at the same time. So let’s see whether there’s any scientific merit to these claims.
Everybody knows chili peppers for their interesting taste, the pungent flavour they add to food, and occasionally, extreme heat. All of these can be attributed to specific chemicals called capsaicinoids. The most known capsaicinoids are called capsaicin and dihydrocapsaicin, and these are the compounds which also give it its specific taste and aroma.
These compounds impact our body because they act on certain receptors that can be found throughout our bodies. As a result, we can perceive pain from the heat and acid, depending whether we are used to eating chili peppers or not. Considering that these receptors can be found throughout our body, it isn’t so surprising that the consumption of chili peppers can have some interesting implications for our health.
The effects of capsaicin
Different studies suggest that eating chili peppers on a daily basis increases the amount of calories we burn after a meal by 30%. They also increase lipid oxidation by around 20% [1, 2]. Moreover, this effect of lipid oxidation seems to be more pronounced in people who tend to be heavier; have a higher BMI.
When it comes to the regulation of energy intake, the results are more mixed. One reason for this is because some researchers only measured what would happen after one meal with capsaicin, while others measured what would happen after an increased number of meals. It seems that eating capsaicinoid pills can cut the amount of calories we consume per meal by around 74 calories. While these results were different whether people were male or female, whether their meal was big or small, or what their ethnicity was, all of them were insignificant when the researchers controlled for dosage – this means the amount of chili people were consuming was the only important part of the effect. 
We can imagine that adding a source of capsaicinoids to every meal would equal to around 220 calories per day if we’re eating three times per day. This means that a simple addition of a source of capsaicinoids with every meal can have impressive health benefits. Moreover, this caloric reduction is around half of the caloric intake that is usually recommended for a healthy weight loss. And we’re not even talking about caloric restriction as a consequence of voluntary choice.
However, there is a lot of variety about the possible required dosages and long-term implications about the amount of chili consumption needed for the mentioned effects. Generally, more than 2 mg of capsaicinoids but less than 10 mg seemed to produce the mentioned health benefits. But we have to understand, as always, that people are different and can have a very different reaction to these compounds.
What is also very interesting is that some evidence even suggests that capsaicinoids have a synergistic effect on weight loss when they are used together with green tea. This only furthers their usefulness as a weight loss supplement when used together with green tea. 
Capsaicinoids seem to exert their effects by decreasing levels of ghrelin and increasing levels of GLP-1. Ghrelin is a hormone responsible for increased appetite as it stimulates hunger, weight gain, and hormone production. GLP-1, however, is an appetite and food intake regulator. [8,9 ,10]
Another possible way is the stimulation of our central nervous system, this in turn causes the release of catecholamines . These are some of the hormones which have a role in the flight or flight response. They reduce our appetite, and through that, possibly the amount of food which we eat when eating capsaicinoids as well. 
Not everyone is a fan of chili and its taste. Adding such amounts of chili obviously depends on the person and his culture. Asian cultures are much more accustomed to chili and can use it in bigger amounts for that reason. However, as we can see it has some nifty properties which can substantially increase the amount of burned calories for your weight loss efforts.