scorecardHow to lose fat and build muscle in 3 simple steps, according to personal trainers
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How to lose fat and build muscle in 3 simple steps, according to personal trainers

Rachel Hosie   

How to lose fat and build muscle in 3 simple steps, according to personal trainers
LifeScience4 min read
  • Losing fat and gaining muscle simultaneously, known as body recomposition, can be tricky.
  • Eating a high-protein diet in a small calorie deficit, strength-training, and sleeping enough are key.

Personal trainers have broken down what it takes to to lose fat and build muscle at the same, to achieve what is known as body recomposition.

As a general rule, to lose fat a person needs to eat fewer calories than they burn, known as being in a calorie deficit, while building muscle requires a surplus.

However, there are certain contexts that make body recomposition easier to achieve, according to Nick Shaw, personal trainer and founder of RP Strength, the official nutrition coaching platform of the CrossFit Games:

  • If you are new to strength training
  • If you are returning to strength training after time off
  • If you have changed your diet to hit the right calories and protein for the first time

Body recomposition is "not the norm" as it's tricky to achieve, Shaw told Insider.

It may be more difficult for some people due to potential barriers such as their genetics, socio-economics status, or mental health, Dr. Mike Molloy, founder of M2 Performance Nutrition, told Insider. But it's theoretically possible for anyone to lose fat and gain muscle.

Here's what personal trainers said you need to nail to give yourself the best chance of achieving body recomposition.

Eat a high-protein diet

Consuming a high-protein diet while in a slight calorie deficit will give you the best chance of holding on to, or even building, muscle while losing fat, research suggests. Don't drop your calories too low though, or you will be more likely to lose muscle, Emily Servante, a certified personal trainer at Ultimate Performance Personal Training, previously told Insider.

One small 2016 study found that men who consumed more protein while also resistance training and doing high-intensity interval training lost more fat and built more lean body mass, which is everything except the fat.

Another small 2018 study of women found that those who ate a high-protein diet while resistance training lost more fat and built more muscle than those who consumed less protein.

A post shared by Ben Carpenter (@bdccarpenter)

Protein helps muscles recover from workouts and is satiating so keeps you feeling full. It also has a higher thermic effect of food than carbs and fats, meaning the body uses more energy to digest it.

Eating at least 0.7 grams per pound of bodyweight daily is enough to maximize strength gains, according to a meta-analysis published on September 4 in Sports Medicine Open, Insider's Gabby Landsverk previously reported.


Resistance training is key for body recomposition.

"Most people focus entirely on the weight loss aspect when trying to recomp," Molloy said. "However, I would argue that most people need to spend as much if not more time putting energy into building muscle mass as well."

While cardio has many benefits for overall health, and any type of movement burns calories, it's not essential for fat loss, Molloy said.

A 2015 meta-analysis found that overweight people who strength-trained lost more fat than those who did cardio.

Another study published in 2021 found that people who mostly did strength-training were less likely to become overweight than people who mostly did cardio.

This is because strength-training causes the body to burn more calories outside of workouts, Molloy said.

Shaw recommends training "like a bodybuilder."

"Make sure you are training with higher volumes in the gym," he said, meaning enough reps, sets, and weight. Shaw suggests sets of 8-12 reps of each exercise with weights that are heavy enough to be challenging.

Continue challenging yourself and stimulating muscle growth by applying progressive overload, which means gradually increasing the reps or weights, he said.

Sleep enough and manage stress

As well as eating well and strength training, recovery is also key, Molloy said.

Molloy recommended sleeping for eight hours a night and keeping stress levels down.

A 2004 study suggested that two nights of less than six hours' sleep could lead to a 25% increase in hunger, and a 33% increase in cravings of ultra-calorie dense food. This is because ghrelin (known as the "hunger hormone") increases when a person is sleep-deprived, the researchers found.

Be patient

Body recomposition is not a fast process, so patience is required, the experts said.

"Unlike weight loss that can be very rapid (demonstrated with the prevalence of hardcore crash diets), building muscle is a notoriously slow process, and, therefore recomping is no different," Carpenter said.

Seasoned gym-goers may get better results in the long-run by having dedicated phases of fat loss or muscle gain, Shaw said.

"Trying to do both can be counterproductive as the best way to lose fat is by eating less and the best way to gain muscle is by eating more," he said.

It's also not possible to choose which body parts you lose fat from, as this largely comes down to genetics.

"People tend to have stubborn areas that, even by training those areas with weights, will still be the last place that you lose fat from," Shaw said. "The best idea is to just slowly get leaner and eventually that stubborn fat will come off."