Building muscle mass while losing weight

My workout

Published on 9 September 2014
by Jean-Denis Thomson

A lot of women hesitate to exercise with free weights when they undertake a weight loss program, for fear that such training will result in muscle hypertrophy and make them look like a bodybuilder.  

Actually, the goal is not to develop muscle, but rather to lose fat! The key to a sound weight loss approach remains cardiovascular exercise. However, training with free weights is an essential part of this approach as long as it does not exceed 40% of the training time. Why? Simply because this type of training promotes the retention of muscle mass, thus preventing the yoyo effect, i.e. rapid loss of weight followed by a regain of usually more weight.

When you undertake a diet that doesn’t include training, at least 25% of the total weight loss comes at the expense of muscle mass. This loss of muscle mass then reduces your basal metabolism at a rate of 33 calories per kg of muscle. Since basal metabolism accounts for over 60% of daily energy expenditure, it is very important to maintain this high metabolism by preserving muscle mass.

Here is an example: you’ve adopted a diet and lost 10 kg; approximately 2.5 kg of this weight loss draw on muscle. This muscle loss reduces your energy expenditure by approximately 83 kilocalories a day. This may not seem like a lot, but after one year, the accumulation of unspent kilocalories represents a shortfall of approximately 4 kg. As a result, if you maintain the same calorie intake throughout the year, you will gain 4 kg.

Muscle training will keep your basal metabolism from slowing down. It is therefore important for you to include or maintain muscle-building exercises in your training program, as part of your weight loss approach. You can stop worrying; you won’t turn into a body-builder.

Jean-Denis Thomson
Kinesiologist, Training Department Director