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Why you need to keep your lean muscle mass for a sustainable fat loss

Updated: May 21, 2020

To many this is kind of a common sense, however why exactly keeping your muscles while losing weight is so important? Is it just because of the looks,strength, athleticism or is it something else in question?

Fortunately, there was a recent study on this topic where they did a retrospective analysis of 209 overweight or obese individuals and compared dieting with and without muscle loss. The results showed that individuals who lost muscle mass during the weight loss phase had higher increases in appetite and a higher rebound effect compared to the individuals with no muscle mass loss. Lets see why is this the case and why it is crucial for anyone trying to lose weight to keep as much muscle mass (preferably even build some) as possible.

The study

Diet, Obesity, and Genes as its called, had a total sample size of 209 participants for body composition analysis, and 40 participants for the secondary where appetite perception was studied. All subjects were between 16 and 65 years old with a BMI between 27 and 45 (all participants were overweight or obese).

The study consisted of an 8 week weight loss period, where participants lost 8% of their body weight, followed by a 26 week maintenance period, where they studied appetite perception. Body composition was measured by DXA.

The two main goals of this study were to:

1. Understand the relationship between the percentage of weight loss as muscle mass and weight regain.

2. Understand how the percentage of weight loss as muscle mass affects hunger and appetite.


A few main factors were looked at as possible predictors of weight regain like age, baseline body fat % and baseline fat free mass (muscle tissue). It was found that age predicted only 1.2 % of the variation in the weight regained, meaning it did not play any significant part in weight regain.

Baseline body fat percentage and fat free mass, however, did play a significant role in weight regain. They found a strong correlation with the amount of total weight loss during the diet, and the amount of weight they regained. This means the more weight you lose, the more likely you are to regain it all back.

However, the second largest predictor of weight regain was the amount of muscle mass you lost during the diet. Loss of muscle mass during the diet predisposes dieters to a larger increases in hunger and desire to eat. You get the same effect with fat loss, mainly through hormones like leptin and ghrelin that increase, or decrease your appetite, however, this effect is even more amplified when you add muscle mass loss on top of it.

What I always teach my clients is that hunger is the number one reason why diets fail, and the key to a successful diet is proper hunger management. This is why fat loss program should always include resistance training to either maintain or in most cases build more muscle tissue.

What is very interesting in this study is that leaner people at the beginning of the study had a higher rebound effect when it comes to weight regain. The explanation is quite simple, leaner people have less fat stores to tap into, resulting in more muscle loss during the diet. This translates into higher hunger and more weight regain after the diet is finished.

On top of resistance training, another important factor is how quickly you lose weight on a weekly basis. Leaner individuals will lose muscle mass even with good workout program in the gym if they go with a big caloric deficit just to get the weight off in the shortest amount of time. This is one of the reasons why I do not recommend going faster than 1.5% per week of total body weight loss. The leaner someone is, the smaller the percentage loss as well to preserve muscle tissue.

Set point theory

A common explanation for weight regain is that everyone has a set point when it comes to body fat %, and that we always strive to go back to that level after the diet. What is actually happening is again very simple. After someone completes a fat loss diet and loses a substantial amount of weight, they eventually go back to their old habits that they had before the diet. This is the typical diet-on-diet off mindset, where people count the days when they are going to finish with the diet. At this point their metabolism has significantly slowed down, especially if they experienced muscle loss (your BMR is literally lower), which predisposes them to weight regain. Since muscle mass takes longer to recover, they will typically overshoot their pre-diet weight and gain even more fat in the process before they regained all muscle tissue.

This is exactly what happened in the Minnesota Experiment where subjects were on a semi-starvation diet for 6 months without any exercise. This was followed by 12 weeks of restricted re-feeding and 8 weeks of ad-libitum re-feeding. They quickly regained all their weight back, however their appetite was still higher than normal because muscle mass takes longer to recover. This resulted in significantly more weight regain in all subjects.


The way to avoid these negative effects of muscle loss and excessive slow down in metabolism is to have a structure when it comes to your caloric deficit, your rate of fat loss, your macro-nutrient balance and workout plan.

First of your caloric deficit will depend on your initial body fat %. For an average individual, this usually translates into 20 - 25% caloric deficit. The easier way to set up your deficit is to track your weekly weight loss and to tweak your deficit until you reach the desired rate. For an average individual this is probably between 1 - 1.5 % of weekly weight loss. Anything more than that will probably result in excessive muscle loss.

When it comes to your macro-nutrient intake, you should aim for at least 1.8 g / kg of protein per day, and at least 20% fat intake of your total daily energy budget. Ideally you can push it even to 30% for maximal effects. The rest of the calories should be filled with carbohydrates.

Workout plan should consist of resistance training for full body with a progressive overload over time. This means you should keep making your workouts challenging either through increasing the weight you lift, or by improving your form, increasing your range of motion, or even adding more sets over time.

If you do these things correctly, you should have a much easier time sustaining your fat loss results over a long period of time. The weight you initially lost is only good if you manage to keep it off.

If you want to take action today and take your fitness to the next level feel free to book a free assessment call with me.

What you will get from this call:

  1. I will see what is your current situation and give you my feedback on what is the best way to go forward.

  2. You will understand exactly what  needs to be done in order to achieve your desired fitness goal.

  3. We will talk about strategies that can help you to reach that goal and how to fit them in your lifestyle.

  4. If we both feel that my program and my coaching is a good fit for you, we can talk about working together.

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