Slowing your metabolism isn’t something anyone wants, especially those trying to lose weight. However, understanding the why can be a little complicated.
To understand how this works, you must realize that just living burns calories, so getting up, breathing, and even going to the bathroom burns calories. What you eat can increase or decrease your energy expenditure for the day. Compared to high-carbohydrate diets, those high in proteins have been shown to speed up metabolism during weight loss because they increase your total energy expenditure, including the energy your body expends just living, according to 2015 research in Clinical Nutrition. Continuing on a high-protein diet, even after the weight is lost, helps keep your energy balanced so the weight isn’t gained back. Research in 2012 in JAMA also backed this up by showing that low-carb diets resulted in the least decrease in resting energy expenditure and total energy expenditure compared to low-fat and low-glycemic-index diets.
All this research has one conclusion: Not eating enough protein can slow down your body’s natural resting expenditure and lead to a positive energy balance, which means a slower metabolism. Meeting or exceeding your daily protein requirements can speed everything back up.