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Why muscle loss ends up as fat gain

man pinching stomach fat

We see many clients at Bodyscan who lose a lot of fat but who also lose a great deal of muscle too.

Sometimes so much that their body fat percentage actually goes up. In other words, body fat now makes up a bigger proportion of their total body weight.

Look at Nikhil, whose results are above. In a Biggest Loser-style, rapid weight-loss programme with a massive calorie deficit, he lost 4.7kg of lean mass to his 4.9kg of fat. Big muscle losses do not bode well for keeping the fat off.

Indeed, loss of muscle is the reason why so many people who shed a lot of weight (see this article about DEXA and Oprah Winfrey) yo-yo back up again, and it highlights the importance of retaining your muscle mass when you embark on a fat loss regime.

Many people assume that when in a calorie deficit your body will turn first to its fat stores to make up the gap. But your body’s survival instinct takes an opposite view. Carrying muscle mass is calorie inefficient; big muscles burn a lot of calories even at rest. That’s why gaining muscle mass takes a lot of time, effort, heavy weights and loads of food.

Fat, on the other hand, is a great store of energy and helped ensure our ancestors’ survival when food was sparse and before there was convenience food within arm’s reach.

The need to survive and the expensive energy requirement of lean body mass is why your body can turn to deplete your muscles – rather than your fat – when you reduce your calorie intake.

The double whammy is that with lower muscle mass your body then burns fewer calories when at rest, so if you break your diet and simply go back to what you were eating before there’s now a bigger gap than there used to be between the calories you’re taking in and the calories you’re burning. Result – ballooning fat.

The statistics vary but a quick flick through a number of articles puts the number of people returning to their starting weight or above after a diet anywhere between two-thirds and 97%.

To retain your calorie-burning muscle, therefore, the best thing you can do it add weight training to your programme. Unlike our big muscle-losers above, other Bodyscan clients have taken our advice and made resistance work a core part of their programmes.

Abigail, shown below, took it slow and steady, with a deficit of 400 calories a day, and regular resistance work. In exactly one year she lost a whopping total of 19kg of body fat with absolutely no loss of lean mass (a small gain of 822g).

DEXA scan images showing fat loss
Abigail, amazing fat loss of 19kg and no lean loss
DEXA data showing fat loss
19kg (18794g) of fat loss, small gain in lean mass of 822g after one year

In our experience at Bodyscan, success is wholly dependent on consistency. There is no point in any diet or exercise programme if you’re not going to stick to it, which is another reason why slashing calories and manic fitness schedules don’t work. In a couple of weeks you’ll be fed up and succumb to temptation. It’s better to plan for slower, more gradual fat loss by restricting calories just 20% below maintenance levels and an achievable exercise and gym schedule. (Note: if you’re gaining fat, you’re already eating above your maintenance calories, so you will need to reduce calories further – first to get to maintenance and then more to achieve a deficit. Check out our body composition calculator for an idea of your calorie requirement.)

For information, the DEXA information video below explains the simple, fundamental difference between fat loss and muscle gain.

If your programme has derailed, it’s probably time to get a new Bodyscan Baseline scan. We’ll give you achievable targets and then measure your progress in 3-4 months’ time. If you’re committed to making changes, then hold yourself accountable with a package of scans over the course of a year – take it slow and steady with regular measurements. Tracking your progress over time, rather than far-apart sporadic checks rapidly increases your chances of success.

Philip Chant

Kevin Garde

Rob Webster