“I read your post about building muscle in a calorie deficit, but I’m still a bit confused,” wrote one Muscle Evo reader.
“I have a belly that I want to lose which I surely can’t do just by focusing on building muscle. But from what I can tell, if I restrict my calories it will affect my metabolism as well as my ability to build muscle.
“I’ve been restricting my calories using an online diet tracker. It seems to be working but I am starting to get the feeling that fat loss is slowing.
“Should I be eating more? Any advice would be appreciated.”
To lose fat, you need an energy deficit.
Putting yourself in that deficit will affect your metabolism in several ways (which I’ll talk more about in a moment). It will also affect your ability to build muscle.
It is possible to build some muscle while you’re in a deficit.
Your ability to do so will be affected by a bunch of factors, including your genetics, your training age, your biological age, as well as the type of training program you’re following (some work better than others).
But your rate of muscle growth will be slower than it otherwise would be if you were eating more.
Which is fine.
Remember, your goal isn’t necessarily to build muscle while you drop fat.
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It’s to retain the muscle you already have.
If you do gain some muscle, great. If your training program is set up properly, I’d be surprised if you didn’t. But think of it as an added bonus, rather than something you should be expecting.
Should you be eating more because fat loss is slowing?
It’s quite normal for your rate of fat loss to slow down over time. Someone who is very fat (think your typical Biggest Loser contestant) will be able to lose fat very quickly when they start dieting – several pounds of fat per week in some cases.
A lean competitive bodybuilder trying to drop from 8 to 6% body fat in the last few weeks before a show is going to lose fat a lot more slowly. If he tried to lose several pounds of fat per week, the large calorie deficit required to do so would result in the loss of muscle as well as fat.
That being said, while it’s quite normal for fat loss to slow down over time, you don’t want it to come to a halt completely.
But eating more calories probably isn’t going to help.
You’ve lost weight. As a result, your body is now smaller. And a smaller body requires fewer calories to maintain it.
Think about it.
If you lose 20 pounds of fat, you have 20 pounds less weight to carry around with you. So it takes less energy to walk up the stairs, run on the treadmill or whatever else it is that you’re doing.
At rest, one pound of fat burns around 2 calories per day. The same amount of muscle burns roughly 6 calories per day. So let’s say that of those 20 pounds you’ve lost, 17 pounds came from fat and 3 pounds came from muscle.
Based solely on the amount of weight lost, you’re now burning around 52 fewer calories per day.
But even that number doesn’t tell the whole story.
There is also a drop in energy expenditure in response to dieting, which is not entirely explained by changes in body composition. This is known as adaptive thermogenesis .
Adaptive thermogenesis is defined as the “decrease in energy expenditure beyond what can be predicted from body weight or its components under conditions of standardized physical activity in response to a decrease in energy intake.”
When observed, it’s been found to range from as little as 79 to as much as 504 calories per day beyond what is predicted from the amount of weight lost .
While a reduction in body mass reduces the amount of energy required to move around, there’s also some interesting research to show that your muscles become more “efficient” in response to weight loss .
In other words, even if you replace the weight you lose by wearing a weighted rucksack everywhere you go, the amount of energy it takes to complete a given task is still going to be lower than it otherwise would be.
Something else to consider is the impact of non-exercise activity thermogenesis, or NEAT for short.
NEAT refers to the calories burned during physical activities other than exercise. I’m talking about things like gardening, doing the housework, or even just getting out of your chair and walking around.
When you go on a diet, there is usually a measurable reduction in NEAT, which also means fewer calories burned over the course of the day .
According to some estimates, a formerly obese individual will require roughly 300–400 fewer calories per day to maintain the same body weight and physical activity level as a never-obese individual of the same body weight and composition .
All of which means that the accuracy of an online diet tracker will change over time. It might start out working just fine. But it can’t predict how your daily energy expenditure is going to change in response to the diet.
In summary, the reason that your rate of fat loss has slowed is that the energy deficit required to lose fat has been substantially reduced or even lost completely.
So you’ve got two options.
You can accept the slower rate of fat loss as normal (which it is). Or you can increase the size of your energy deficit by burning off some more calories or cutting back a little more on your calorie intake.
Of course, this isn’t the right approach for everyone.
If you’re already eating a very low level of calories, your weight loss has stalled, and you’re going crazy with food cravings, then eating less is most definitely not the way forward.
But if all that’s happened is that you’re now losing fat more slowly than you once were, and you want to speed things up a little, a few tweaks to your diet and/or activity levels should be enough to get things moving again.
1. Tremblay A, Royer MM, Chaput JP, Doucet E. (2013). Adaptive thermogenesis can make a difference in the ability of obese individuals to lose body weight. International Journal of Obesity, 37, 759-764
2. Helms ER, Aragon AA, Fitschen PJ. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11, 20
3. Trexler ET, Smith-Ryan AE, Norton LE. (2014). Metabolic adaptation to weight loss: implications for the athlete. Journal of the International Society of Sports Nutrition, 11, 7
4. Rosenbaum M, Leibel RL. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34, S47-55
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