Why does lost weight come back so quickly? Simple. Being on a diet, the more weight we lose, the lower the basal metabolic rate (BMR), which is the energy needed to maintain the body at complete rest. That is, the more weight we lose, the less energy our body consumes. Thus, eating the same amount of calories brings back lost weight. The opposite is also true. The more weight you gain, the higher the BMR (you must eat more to maintain the new weight). In addition to being on a diet, excessive aerobic exercise causes muscle lost, which also reduces the BMR. |
The highest contribution to BMR - from 60 to 80% - is lean mass (fat free mass), which can be only increased by gaining muscle. Muscle burns 3-5 times more calories than fat does, so doing lots of aerobic exercise promotes fat loss but also muscle lost, which highly reduces the basal metabolic rate.
Other factors that affect BMR include fat mass (6.7%), age (1.7%) and sex. As previously explained, losing fat decreases the BMR, which makes easier regaining lost weight. BMR also depends on sex, as women have higher proportion of body fat.
So, what can we do to prevent from gaining back lost weight? There are few ways to boost the metabolism. First, you can eat the same amount of calories but in 5 meals a day, as digestion boost the metabolism for few hours. However, take into account that the person who wants to gain weight also eats 5 or more times per day but a much higher amount of calories. So, just make smaller meals during the day (see Nutrition Tips).
Second, if you are on a diet, make sure you also exercise, and that the exercise you do stimulates muscle tone. Avoid repetitive aerobic exercise that may lead to muscle lost, change exercises and go for high intensity interval training for better results (see HIIT). Bodyweight training just 2 or 3 times a week for around 20 minutes per day is enough to build muscle; you will also look better with more muscle tone. Thus, an increase in lean muscle helps to compensate the decrease in BMR due to weight loss.
Third, high intensity interval training boost your metabolism from 2 to 24 hours to replete the ATP (cell's energy) and glycogen, repair muscle and tendon tissue, and make changes in nervous system (see Why Bodyweight Training). It was shown to be nine times more efficient for fat loss than aerobic exercise (for further details see M Lauren, You are Your Own Gym).
It is more effective to workout large muscles. What are the largest and strongest muscles in the body? In the legs we find the largest and also one of the strongest muscles: the glutes. Also the quads and biceps femoris are large muscles, which make leg training very effective to maintain weight. Go also for the lats and other back muscles and chest (see Bodyweight Exercises).