I’m going to inject a little realism into your world — you could lose 15 pounds of weight (~7 kg), but your body composition may be worse off.

You see, weight loss is often accompanied by a loss in lean body mass — muscle tissue and its transient contents. This loss in lean body mass has multiple negative health implications one of which being a subsequent body fat overshoot aka weight regain.

This is because less lean body mass means lower resting energy expenditure aka “slower” metabolism.

Now, for purposes of description, enjoy this view:

This is the Minnesota Starvation Experiment during which conscientious objectors of war went through 24 weeks of semi-starvation study — their calories were cut by about 50%.

Folks probably whined, wheedled, complained, and yet each of them had to go through the trial to lose about 25% of the original weight. They reached the limits of human leanness of 4-5% body fat.

But here is the interesting part:

The subjects were put on 8 weeks of ad libitum refeeding phase during which they regained all the fat that they have lost. But it didn’t stop there, my dear internet human — they kept gaining fat until… they regained lost muscle mass:

The relationship between muscle loss and fat regain

So if you want to have a successful weight loss, don’t be the individual who only cares about the number on the scale. Even more important than overall weight loss is sustainably losing fat mass while maintaining lean body mass.

This is why I have done some digging on your behalf and found the study that looked at popular diets and their ability to preserve lean body mass. Here are the diets that researchers looked at:

1
Very low calorie diet

Very low-calorie diet often includes a drastic reduction in calories. Usually to 400-800 kcal/day. Makes you drink meal replacement powders, smoothies, liquid lettuce, and similar shit which you would never drink under your own will.

With such a drastic cut in calories comes equally drastic consequences:

You would never recommend your best friend to live off 800 calories (unless you hate your best friend and your best friend is actually not your best friend but rather your fiercest enemy who slept with your significant other multiple times and took your favorite Def Leppard albums).

So don’t do it yourself. You are not gaining anything by losing a lot of weight quickly.

As Jordan Syatt wrote, “a good calorie deficit doesn’t entail eating as little as possible to lose weight as quickly as possible. A good calorie deficit allows you to eat as much as possible to lose weight as sustainably as possible.”

2
Low carb/ketogenic diet

I think keto diet is stupid for most people because most people love carbs. We would never give them up, right? Our precious…

Also, a recent review of 13 ketogenic diet studies found that 20–25% of weight lost was from lean body mass:

Keep in mind that we have very few studies combining resistance training with keto. Resistance training has shown an impressive ability to maintain muscle mass and I’m pretty confident that keto diet combined with resistance training would maintain lean body mass pretty well.

This doesn’t change my mind that keto is deeply stupid. Here is my reasoning:

At seminars, Alan Aragon, nutrition researcher, often asks people to raise their hands if they tried keto diet. A crapload of hands goes up. He then asks to keep arms raised for those who are still on keto. Most hands drop.

Keto is very rigid and therefore, it’s hard to sustain for a long period of time. Any diet that you cannot adhere to long-term is just not a healthy diet.

But if you can adhere to it, kudos to you, go for it. Lift weights along with it and you probably will be fine.

3
Low fat diet

The idea behind low fat diet is to reduce the intake of the most energy-dense macronutrient — fat (9 kcal/g as opposed to protein and carbohydrate coming with 4 kcal/gram each).

However, reducing fat doesn’t seem to do well in terms of muscle retention:

Also, low fat diet tastes like cardboard as most yummy foods contain a hefty amount of fat:

4
High protein diet

Protein consumed at double the RDA recommendation (1.6 g/kg or 0.73 g/lb) repeatedly outperformed the RDA (0.8 g/kg or 0.36 g/lb) for maintaining lean body mass and reducing fat mass.

Since protein induces muscle protein synthesis — the process of building new muscle — it’s no surprise that it does well in preserving lean body mass:

In Demling and Desanti’s study, subjects on a high protein diet combined with resistance not only maintained but also gained muscle mass. In the same line of thought, Carbone et al. concluded that:

The newest research confirms that consuming higher-protein diets, particularly when coupled with resistance exercise, preserves muscle mass and maintains whole-body protein homeostasis during moderate energy deficits.

So, 1.6-2.2 grams of protein per kilogram of body weight (0.73-1 g/lb) spread out over 3-5 meals will keep you from becoming like that Gollum dude saying “my precious.” Shame on you if you have never seen Lord Of The Rings.

5
High fiber diet

It has been theorized that the type of carbohydrate may cause greater weight loss, better satiety, and muscle retention. But it didn’t.

The type of carbohydrate — whether it’s “complex” or “simple” — didn’t cause greater weight loss nor did it do well in maintaining lean body mass:

Further reading: Complex carbs aren’t better than simple carbs for fat loss
~
Now, this review didn’t investigate intermittent fasting. So I feel like it’s my duty to fill the gap because more and more people are “skipping breakfast” and calling it “intermittent fasting.” So…

6
Intermittent fasting

Time-restricted eating and alternate-day fasting are all the rage these days so let’s focus on those two.

Fasting for about 16 hours seems to have a good track of lean body mass retention when combined with resistance training:

Results suggest that intermittent fasting paired with resistance training generally maintains lean body mass and can also promote fat loss.

Moro et al. also looked at the 16/8 fasting protocol (a 16-hour fasting window and 8-hour eating window) and came to the same conclusion — intermittent fasting coupled with resistance training maintains lean body mass just fine:

Intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.

Now, if time-restricted eating has repeatedly shown muscle retention, alternate-day fasting has routinely shown the opposite — the loss of lean body mass.

There is an overwhelming body of evidence that has shown just how easy it is to lose lean body mass if you fast for too long. This happened time after time after time. I can do this all day. Here is one more.

So, trying to crush world fasting records as if they were eggshells is probably not the best idea. Keep your fasting window to 16 hours tops (shorter for women). Also, lift weightz.