Building muscle in a calorie deficit - goes

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Richard Staudner

The Optimizer

Can I also build muscle and lose weight at the same time? So in the calorie deficit achieve muscle growth? Generally there is this separation of bulk and cut. If you want to build muscle and strength, you need bulk phases, after which you can lose weight again. But is it possible without it? A large meta-analysis has dealt with this.

Building muscle in a diet? How nice would that be? At least for strength athletes or bodybuilders, it sounds like fiction. But is it possible with the right strategy?

Let's take a look at the relevant biological processes in our body. During calorie restriction, i.e. reduction of food intake, the production of anabolic hormones, such as IGF-1, is inhibited. This process also has an influence on muscle growth. After only 3 days of caloric deprivation, the physical response to strength training is reduced. In addition, a lack of energy has a negative impact on sexual and metabolic hormones. This not only affects our libido, but also becomes noticeable through poor bone health or amenorrhea (loss of menstruation in women). However, what about when caloric restriction is followed through for an extended period of time? Does the body eventually adjust to the state of deficiency?

The recently published work from Munich summarizes results from 52 studies. Two different types of statistical processing were chosen. The exact structure is a bit too detailed for this Newsflash, we preferred to look at the conclusions:

The researchers found for the first time clearly that the muscle gain is greater without calorie restriction than with. That's probably not surprising. More food, more muscle! However, depending on the statistical analysis, the effect on lean mass was even significantly negative. That is, the participants actually lost muscle mass. What is interesting, however, is that strength increased despite the lack of energy. This could definitely be interesting for both weight training and bodybuilding. More strength is definitely a desired effect in these sports.

The researchers also found that from a deficit of about 500kcal daily, muscle mass maintenance is no longer possible. The body now uses muscle as an energy reserve and burns it. If the deficit is smaller than 500 kcal, the meta-analysis also found a possible increase in muscle mass, but significantly less than without calorie restriction. So yes, muscle gain is indeed possible. Whether this makes sense is an individual question.

However, there are 2 difficulties in interpreting the results:

  1. For diet, only the prescribed amount of calories was compared, not the actual amount consumed, and often activity throughout the day was not collected to calculate energy needs. This means that the energy deficit data is somewhat inaccurate. There is also a lack of information on protein intake, which has a significant impact on muscle growth through strength training.
  2. The second, perhaps even more important thing: the age of the participants. They are on average 60 years old (+-11 years) and only one of the studies involved athletes with previous experience in strength training. According to the authors, this could also explain the increase in strength. With training beginners often microarchitectural changes in the muscle structure, or neuronal adaptations are to be recognized, which brings a better control and use of the muscles with itself. Without mass gain, the strength grows. Since a large proportion of the study participants were not regularly strength training prior to the study, this would be an explanation for the increase in strength. In only two of the studies examined was a negative effect on the strength to recognize and one of them is exactly the only study with athletes with previous experience in weight training.

Explicitly, the authors say, "It is unclear whether the associations would be in normal, experienced weightlifters:in because not enough data [...] exist."

So clearly, if you want to gain muscle, you should avoid calorie restriction, or keep it as low as possible. But no one can promise that you will be successful with it. 200 calories would be a good starting point to test this and gain experience.

And when you restrict energy intake, you should not forget what a stress this is for the body: state of alarm, fight for survival. Instead of restrictive diets, one could, for example, consider various forms of fasting. So temporarily reduce calories completely to zero. This is also relatively stressful, but the health effects are definitely relevant for us. But that probably goes too far for today's topic and will be explained in another focus.

The study is 'open access', meaning it is available for free and can be read by anyone...: Murphy, C. and Koehler, K. (2022) 'Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression', Scandinavian Journal of Medicine & Science in Sports, 32(1), pp. 125-137. doi:10.1111/sms.14075.


Richard Staudner

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