31/03/2025
HOW TO LOSE FAT WITHOUT LOSING MUSCLE.
NEVER START CUTTING FOOD INTAKE.
Chris Masterjohn, PhD
When you “lose weight,” the health benefits you get are from losing fat.
These are directly opposed by losing lean mass, which includes weight from muscle, bone, and internal organs.
There is such a thing as losing too much fat.
For the average woman, the threshold is probably somewhere around the 17-22% body fat range.
For the average man, the threshold is probably somewhere in the 6-12% body fat range.
Everyone has their own unique optimal body fat, and that optimal point will vary according to the demands of your life, so always judge your results by whether you are getting healthier or not.
But if you choose to lose weight, you have to focus on losing fat, not muscle.
Unfortunately, the average person who cuts calories to lose weight will lose between 40% and two-thirds of that weight as lean mass. This ratio is HORRIBLE.
There is no need whatsoever to lose as much or more muscle as fat, and this shows you that standard calorie-cutting is a tremendously bad way to lose weight.
So how do we preserve lean mass when losing weight?
Three rules:
Exercise more, do not eat less. If you eat junk food, stop, and eat good food. If you are stuffing yourself silly and in an inexorable path toward greater and greater obesity on a daily basis, stop, and eat normal amounts of food. If you are currently eating good food that is keeping you weight stable, do not start by eating less. Rather, get your total resistance training and high-intensity workouts up to six hours per week with the base of this being full-body resistance training and the remainder high-intensity intervals and sprints. Add some moderate intensity work on top of this base and lots of light activity like walking. If you are able to recover from this exercise and feel good, and you are not losing weight fast enough, add more activity. If you hit a wall where you are exceeding your recovery capacity, then it is time to cut food intake.
Eat enough protein. Obtain 1.2-1.8 grams of protein per pound of bodyweight (0.55-0.82 grams per pound of bodyweight). If you insist on losing weight faster than one pound per week, get your protein up to 2.4 grams per kilogram bodyweight (1.1 grams per pound of bodyweight) per day.
Slower is always better. If you hit the exercise target above and hit the 2.4 g/kg protein target, you can lose up to 1.6 pounds per week and expect to gain muscle, or you can lose up to two pounds per week and expect to retain all your muscle. If you hit the exercise target above and get 1.2-1.8 g/kg protein, you can expect to retain all your muscle if you keep your weight loss down to 1.6 pounds per week and possibly gain muscle if your keep your weight loss down to 1 pound per week. If you do not follow the exercise or protein targets above, you must limit your weight loss to one pound every three to four weeks, and you should expect to lose 14-20% of. your weight as lean mass.
These rules should allow you to retain most of your muscle mass or possibly even increase it while losing fat.
If the only tool you wield is keeping weight loss to no faster than one pound every three to four weeks, you will probably lose 15-20% of your weight as lean mass.
There is no amount of protein that will completely stop you from losing lean mass.
The ONLY thing that will stop you from losing any lean mass is the exercise recommendation in the second bullet point. NO EXCEPTIONS.
Here’s the data to back this up.
In obese postmenopausal women losing weight over five weeks, those who lost less than 0.74 kilograms (one-third of a pound) per week lost only 14% of their weight as lean mass, while those who lost weight faster than that lost 50% of their weight as lean mass.
An earlier study in women found no difference in 1.1 and 1.9 kilograms per week (0.5-0.85 pounds per week, but 43% of weight loss was lean mass.
In 126 obese men and women who lost weight over 6 months, those who lost more than ten percent of their bodyweight lost an average of a half pound per week, 20% of which was lean mass; those who lost between three and ten percent of their bodyweight lost an average of a quarter pound per week, and it was only 12.5% lean mass.
These studies indicate that one third to one quarter pound per week, or one pound every three to four weeks, can keep the lean mass loss to 14-20% instead of 43-50%.
A half pound per week is in a gray area.
When resistance training is limited to three days a week, the effect of protein maxes out at 1.6 grams per kilogram bodyweight and about one-third of weight lost will be lean mass on a 40% caloric deficit. Consuming the RDA for protein — 0.8 grams per kilogram of bodyweight or 0.36 grams per pound of bodyweight, led to nearly double the rate of lean mass loss. However, increasing the protein to 2.4 grams per kilogram did absolutely nothing to stop a third of the weight loss being lean mass.
This indicates that more protein can allow you to lose weight faster, but the maximal effect of protein is to make you lose one third instead of two thirds of your weight as lean mass on a rapid weight loss program.
If the same caloric deficit is paired with working out for six days a week in a mix of resistance training, sprint intervals, high-intensity interval training, plyometrics, a cycling time trial, and ten thousand steps per day, lean mass stays constant on 1.2 grams per kilogram bodyweight and lean mass is gained on 2.4 grams per kilogram bodyweight).
The 40% caloric deficit led to weight loss at a speed of 1.6 pounds per week.
This is the exercise protocol that allowed subjects to gain lean mass while losing fat mass:
There is no evidence from this study that the particularities drive the effect. Most likely, resistance training is the most preserving of lean mass due to the anabolic effect. However, it is also good to engage different intensities of cardiorespiratory fitness for general health.
In elite male and female athletes doing an average of 14.6 hours of sports-specific training per week and doing resistance training four times per week practicing progressive overload, and consuming 1.2-1.8 grams of protein per day, a weight loss program lasting four to twelve weeks until the target was reached caused lean mass to stay the same when weight loss was 1.4% of bodyweight per week (for example, a 150-pound person losing 2.1 pounds per week), but go up when weight loss was limited to half that (close to one pound per week).
This indicates that exercise is far more powerful than protein in minimizing lean mass loss, and is the only tool in the kit that can completely prevent lean mass loss and even lead to lean mass gain while fat is being lost.
Synthesizing these last two studies suggests that once you hit the threshold for sufficient exercise (somewhere around six hours per week of resistance and high-intensity work) and consume at least 1.2-1.8 grams per kilogram bodyweight protein, you should retain all your lean mass and effectively have two options to achieve an increase in lean mass:
Slow the total weight loss to one pound per week.
Increase your protein to 2.4 grams per kilogram bodyweight per day.
Lose fat, not muscle. 👊
