Weight loss is hard and keeping it off is even harder. Your body is designed to fight weight loss. Learn the key role of muscle in long term success.
Q: What happens when you go on a very low-calorie diet or have weight loss surgery -- which also results in very low-calorie intake?
A: To answer that question, understand your body’s sources of fuel (or energy). On very low calories, your body goes into starvation mode. Your body needs fuel to survive.
Fuel comes first from food. Then comes stored fuel.
When you eat less food than your body needs to maintain your weight, then the body turns to using stored fuel. Fuel is stored in 3 places in the body:
- Glucose is stored in the liver and muscles. You have about a 24-hour supply of stored glucose.
- Muscle tissue can be converted to glucose.
- Fat stores can be converted to ketones and used as fuel.
First your body uses up all the glucose stores and some fat stores. Starvation mode starts when all the stored glucose is used up -- about 24 hours after you start the low-calorie diet.
Where does your body get glucose now? The body breaks down mostly muscle tissue to make glucose, along with some fat, for fuel.
- BACKGROUND TIP #1: Why do you lose weight quickly when you start a low-calorie diet? Muscle tissue is about 75% water by weight, while fat tissue is only about 10% water by weight. The scale shows that you have lost a lot of weight, but most of the loss is water weight -- as part of the muscle loss.
After a week or more, the body will adapt to using more fat stores and less muscle tissue for fuel.
- BACKGROUND TIP #2: Most low-calorie diets result in loss of both body fat and muscle mass. Here is the key thing: You need to keep muscle because muscle burns calories, day in, day out. Stored fat does not burn many calories. If you lose a lot of muscle mass, then your body needs even fewer calories to maintain current weight.
To succeed long term, the goal is to preserve muscle mass and use fat stores for fuel. Studies[i] show that eating 25-30 grams of high-quality protein at each meal provides the body with the best chance to make and preserve muscle mass.
Regular exercise matters to build muscle mass. When you do exercise, try to follow it with a serving of high-quality protein. We have reviewed the research and concluded that whey protein isolate is the best choice. It is highest in leucine, which helps your body repair and build muscle after exercise. If you have questions, please email firstname.lastname@example.org
[i] We reviewed the research, including the two studies below, carefully because only some of the studies show that higher protein intake preserves muscle mass - even with exercise. The key to success seems to be the quality of the protein and the amount of leucine at each meal.
NOTE that whey protein has the highest leucine content of any protein.
Jung Eun Kim, Lauren E. O’Connor, Laura P. Sands, Mary B. Slebodnik, Wayne W. Campbell, Effects of dietary protein intake on body composition changes after weight loss in older adults: a systematic review and meta-analysis, Nutrition Reviews, Volume 74, Issue 3, March 2016, Pages 210–224, https://doi.org/10.1093/nutrit/nuv065
Amely M Verreijen, Sjors Verlaan, Mariëlle F Engberink, Sophie Swinkels, Johan de Vogel-van den Bosch, Peter JM Weijs, A high whey protein–, leucine-, and vitamin D–enriched supplement preserves muscle mass during intentional weight loss in obese older adults: a double-blind randomized controlled trial, The American Journal of Clinical Nutrition, Volume 101, Issue 2, February 2015, Pages 279–286, https://doi.org/10.3945/ajcn.114.090290