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How to keep muscle when losing fat

For most people, losing body fat is the quickest way to improve body composition and overall health. Achieving a low level of body fat will improve not only the visual aesthetic but also contribute to a reduction in harmful, visceral (internal) fat.

The issue that most face when trying to achieve this is how to maintain the muscle mass they have built up. Muscle-building is a slow, hard progress, so to see muscle disappear is dispiriting to say the least.

The most sensible step you can take to preserve lean mass when shedding body fat is to slow the rate of fat loss. The risk of muscle catabolism (muscle breakdown) goes up when you lose weight (body mass) at a faster rate. A faster rate will negatively alter the balance of muscle-to-fat loss. By slowing the rate down you can ensure maximum retention of lean mass. I recommend a rate of 0.5kg (just over a pound) of fat loss per week achieved through a sustainable calorie deficit of 550 per day.

It becomes even more important to slow the rate down as you achieve lower levels of fat. As well as being negatively impacted by rapid weight loss, muscle breakdown is inversely proportional to your total fat mass – ie, the leaner (lower fat) you get, the higher the risk of losing muscle.

So when you have more fat to lose, you can afford a faster rate without sacrificing much muscle, but as that total fat comes down, you cannot continue at the same rate. The rate must be adjusted proportional to your total fat mass. 

Take a look at the (overall amazing) results for Bodyscan customer Jim below. In his first five months, he lost 20kg of fat (more than half of what he started with) and just 1kg of lean mass (a fat-loss-to-muscle-loss of 20:1). But four months after that the ratio had shrunk to just 2:1 (5.2kg of fat and 2.6kg of lean).

The graph on the left shows the three scans; the rate of fat loss (yellow) slows down while the rate of muscle loss (blue) accelerates. The tables on the right show the details for fat and lean mass, with the earliest scan at the bottom of each table and the most recent at the top. In each table look at the numbers in the far right column (‘change since previous scan’) .

Work to preserve muscle
The second thing you should be doing is resistance training throughout your calorie deficit to hold on to muscle. With an optimised programme of weights, calorie deficit and protein consumption you could actually increase muscle while losing fat. Or you could retain what you have or keep losses to an absolute minimum.

Without weight-training, it’s typical for Bodyscan customers to lose 1kg of lean mass for every 3kg of fat. Work hard in the gym against with a small calorie deficit and you can halt muscle loss completely. Download our muscle guide to see what makes a great weights regimen.

So, in summary, to preserve your hard-earned muscle:

  1. Aim for a maximum rate of loss of 0.5kg per week
  2. As you reduce fat, consider slowing the rate to further preserve lean mass
  3. Work hard in the gym

Rob Webster
Bodyscan Consultant