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Lose Fat And Build Muscle Simultaneously?

Gaining muscle on a weight loss diet is not only possible, it should be expected for most people on a serious program.

We’ve always thought it is impossible to Lose Fat and Build Muscle at the same time but a new study done by Menno Henselmans of proves otherwise. Let’s see what he has to say about this.

Can You Gain muscle And Lose Fat At The Same Time?

We live in sad times for bodybuilding. Although broscience is finally losing face, it’s being replaced by what I can only describe as bodybuilding nihilism (‘nothing-ism’). Nothing supposedly matters. Nutrient timing? Just eat when you feel like eating. Full-body or split training? Whichever you prefer. Eating clean? Bro, what has washing your food got to do with anything?

Skepticism is great, but it’s turning into pessimism that’s killing the spirit of bodybuilding to always keep improving and always push the limits. The nihilism that nothing matters has taken the meaning that nothing works. When nothing works, nothing is possible. If somebody gains muscle during their contest prep, he is immediately accused of steroid use. That’s because many people believe you cannot build muscle and burn fat at the same time. Others say it’s theoretically possible, but it won’t ever happen in anyone but absolute beginners and steroid users. And yet others say body recomposition programs are the best way to progress and you shouldn’t cut or bulk as a natural lifter.

Let’s look at the facts.

The First Law of Thermodynamics

You’ve probably heard someone argue that achieving muscle growth and fat loss in the same day is physically impossible because of thermodynamics. The argument goes as follows.

  1. To build muscle, you must store energy. To lose fat, you must burn energy.
  2. When you are in energy surplus, your body stores energy. When you are in a deficit, your body loses energy.
  3. Therefore, you must be in energy surplus to gain muscle and in a deficit to lose fat.

The first two points, the premises, are true. They refer to the first law of thermodynamics (‘movement of energy’), also called the law of the conversion of energy. This law means energy cannot just disappear. It has to go somewhere. Building new fat or muscle cells requires energy and breaking them down releases energy. However, point three, the conclusion, is false.

Why? Because protein and fat are completely different functional compartments in the body. As a result, your body directs calories towards muscle and fat mass independently. Researchers call this calorie partitioning and the resulting change in fat and muscle mass are expressed as a P-ratio.

Concretely, your body needs protein and energy to build muscle tissue. If it gets enough protein from your diet, it just needs energy and this energy can be obtained from fat mass. The result is simultaneous fat loss and muscle growth.

Similarly, your body is capable of storing fat while burning muscle. The conservation of energy law only means that you must gain energy in energy surplus and lose energy in a deficit. It says nothing about how these calories are partitioned or about how your body composition changes.

In conclusion, thermodynamics do not rule out the possibility of getting more muscular while leaning out at the same time.

Outside the textbook

Theory is nice and all, but what happens in real life? Do people actually manage to build muscle while losing fat?

Overweight (26% body fat) police officers starting a weight training program lost 9.3 pounds of fat and gained 8.8 pounds of lean body mass in 12 weeks.

But they were fat, so how is that relevant for us? Ironically, it’s usually the self-proclaimed science-based skeptics that say you can’t build muscle and lose fat at the same time. Yet people in dozens if not hundreds of studies lose fat and build muscle at the same time when they start training, even sometimes when they only do endurance training (see here and here and here, for example). Young, old, healthy, unhealthy, male, female, obese, lean, they all achieve body recomposition. Even on mediocre training programs with crappy diets with suboptimal protein intakes. Even elderly men and women over 60 years old generally gain around 4 pounds of lean body mass with the same amount of fat loss in 12 to 16 weeks (see here and here, for example).

But all these people were barely trained, so again how is that relevant for us?

Here’s an example of one of Menno’s clients that had over 20 years of training experience and was already benching 235 lb (107 kg) for 5 reps before the coaching. He performed a DXA scan every ~3 weeks during my coaching. In 2 months and 18 days, he lost 6.7 lb (3.1 kg) of fat while gaining almost exactly the same amount of muscle. His weight during the last scan was within 8 grams of his weight when we started. So this is an example of virtually perfect body recomposition. You can find the anonymized DXA scan overview here and his progress photos below.


Still not convinced? Ok, there’s plenty of research in advanced trainees too.

One study looked at elite gymnasts. These were national level athletes with a training volume of 30 hours a week. They could do 17 pull-ups where their chest touched the bar (try doing 1). They were put on a 1,971 calorie, ketogenic diet. In case it wasn’t obvious, that’s pretty drastic for someone training over 4 hours a day. Their fat percentage of 7.6% dropped to 5% – lower than many bodybuilders in contest shape – in 30 days. Even under these conditions, they gained 0.9 pounds of lean body mass. And don’t forget they must have lost a lot of glycogen and water eating just 22 grams of carbs a day.

Similar findings of positive body recomposition have been found in elite athletes of various other sports, including elite rugby players and NCAA Division football players already squatting over 382 lb (174 kg) and benching over 289 lb (131 kg). I personally observe this routinely in my clients. Several of my clients with access to reliable body fat measurement techniques, such as DXA (think ‘x-ray’) scans, gained muscle all the way up until the last few weeks before their contest.


Gaining muscle on a weight loss diet is not only possible, it should be expected for most people on a serious program. As long as the stimulus for muscle growth is carefully designed and customized, your body will find a way to get bigger. Your body is not the enemy. It is a miraculous survival machine that adapts to the stress you impose on it. When you understand it, you can control it.

So screw the naysayers. When you don’t believe what you want is possible, you have defeated yourself before you even began.

Written by Damn Ripped!

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