Estrogen plays a role in how body fat is distributed. When estrogen levels drop in females, visceral fat increases more than subcutaneous fat.
Fat loss occurs when more calories are expended than consumed.
There are three components of total daily energy expenditure: the thermic effect of food (i.e., the energy cost of the digestion, absorption, and storage of dietary macronutrients), basal metabolic rate, and physical activity, which can be subdivided into volitional exercise and nonexercise activity thermogenesis (i.e., the energy expended performing common daily activities such as standing, walking, and fidgeting). For fat loss to occur, energy intake must be less than energy expenditure.
There are no meaningful differences in fat loss between diets that vary in carbohydrate and fat content, as long as their protein and calorie content is equal.
Nonetheless, certain dietary factors can influence fat loss via their effects on energy expenditure, hunger, and satiety, and thus energy intake. These include ultraprocessed foods, which have been shown to increase ad libitum energy intake; protein, which has the highest thermic effect of food among the macronutrients, helps to preserve muscle during weight loss (and thus preserve basal metabolic rate), and may reduce hunger and prolong satiety; and fiber, which may also reduce hunger and prolong satiety.
Supplements of interest for fat loss typically either increase total daily energy expenditure, suppress appetite, or increase the rate at which fatty acids are released from fat cells. The following are some of the most popular supplements related to fat loss:
- green tea catechins
- Green coffee extract
- garcinia cambogia
Most supplements sold for fat loss are ineffective or there’s not enough evidence in humans to support their efficacy, and some can even be harmful. For example, yohimbine, ephedrine, and caffeine can all induce anxiety in some people.