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Rapid Weight Loss

Most people don’t realize this, but you have the option to lose weight quickly. You can accomplish this by eating a lot less.

Normal-weight people can survive around 60 days without a single calorie before starving to death.1408 60 days. Heavy people can last far longer than that.1409 Fat is just stored energy, after all. Remember that the next time you worry about missing a meal.

The higher your total daily energy expenditure (TDEE) soars over your calorie intake, the faster you’ll lose weight. Taken to its logical extreme, the quickest short-term weight-loss strategy is to significantly cut your food intake, and exercise a lot more. Summon the willpower to do this, and you will lose weight quickly.

Health Risks?

In general, the health risks of eating a lot less are greatly exaggerated. Even water fasting (consuming nothing but water) for long periods of time does not usually lead to any health complications. According to one scientific review,

Prolonged fasting is generally well tolerated with few and relatively minor complications.1410

For example, in a 1968 study of 46 obese people who water-fasted for two weeks, no serious medical complications occurred.1411

46 people. Two weeks. No food.

No medical complications.

I’ve talked to many people who have fasted for long periods, and have never heard of any serious complications. (Though pregnant women should probably avoid fasting, and diabetics should be cautious.1412)

In my experience, fasting feels healthy, not unhealthy.

Lose Muscle?

In general, the risk of losing muscle from eating a lot less is greatly exaggerated. After three to four days of total starvation, it’s estimated that a man will lose a gram of muscle for every 2.4 grams of fat he loses.1413 But the vast majority (over 70%) of the weight he loses is still fat.

As the fast progresses, his muscle loss will shrink even further. Eventually, he’ll lose a gram of muscle for every nine grams of fat he loses.1414

In any case, the average muscle loss from all-out fasting isn’t much worse than traditional weight-loss diets. In the average successful diet, around 20% to 27% of total weight loss is muscle.1415

Muscle loss may be a concern if you’re already very lean, but think about it: fat is just stored energy, right? When the body needs energy during a fast, why would it preferentially break down muscle if it’s still got plenty of fat?

That wouldn’t make sense.

And that’s not what your body does. According to a biochemistry textbook:

Proteins are not stored, so any breakdown will necessitate a loss of function. Thus, the second priority of metabolism in starvation is to preserve protein, which is accomplished by shifting the fuel being used from glucose to fatty acids and ketone bodies.1416

Fat—not protein—is the primary energy source your body uses during major calorie deficits.

If you’ve got visible fat to lose, you have little reason to worry that your body will cannibalize all your muscle.

Starvation Mode?

In general, the risk of entering “starvation mode” from eating a lot less is greatly exaggerated. Contrary to popular belief, when you stop ingesting calories (water fasting), your metabolism doesn’t slow down for quite some time.

After 21 days of water-fasting every other day, the 16 subjects of a 2005 study did not experience any slowdown in basal metabolism.1417

In a 1994 study, the metabolic rates of 29 subjects did not decrease between 12 hours and 36 hours of fasting (in fact, they slightly increased, though not significantly).1418

In a 2000 study, after four days of water fasting, the resting metabolic rates of the 11 subjects were increased by 10%, 13%, and 12% after two, three, and four days of fasting, respectively.1419 Small increases in metabolic rate after a 48-hour fast were also shown in a 1990 study.1420

If anything, then, short-term fasting speeds up your metabolism. The idea of “starvation mode” came from studies of prolonged, intense calorie restriction—20 days of water fasting,1421 for example, or three to six months of severe dieting.1422

These studies showed significant metabolic slowdown, but they’re not relevant for the average person eating a lot less for a week.

Gain It All Back? Unhealthy?

Finally, in general, whether a person “gains all the weight back” is determined by their habits. (Although people who have lost a lot of weight have slightly slower metabolisms than weight-matched people who haven’t.1423)

Gaining all the weight back is in no way inevitable. Eating a lot less is what worked for me, for example. I summoned oceans of willpower, ate a lot less, and exercised a lot more. I even started to perceive hunger as a tool of transformation, rather than a nagging pain. Hunger went from being a signal to eat, to a signal that my body was eating fat—and that I was accomplishing my goal. I learned to relish hunger.

This short-term, extreme mindset was extremely effective. I lost over 30 pounds in under a month. (And another 20 pounds the next month.) Aside from some relatively minor fluctuations, I’ve kept them off ever since.

(I stopped drinking sugary drinks.)

Was losing weight that quickly “unhealthy”? It certainly didn’t feel that way. More than anything, it felt spiritual.

And in hindsight, having kept the weight off for a decade, that short period of rapid weight loss seems to be one of the healthiest things I’ve ever done.

Despite the popular belief that losing weight quickly is “unhealthy,” it’s really only losing weight quickly in the context of yo-yo dieting—quickly losing and gaining and losing and gaining lots of weight—that is considered unhealthy.

But a 2014 review of 20 studies concluded that there was “no evidence” that a yo-yoing weight was any worse for your health than staying overweight or obese.1424

It’s not like it’s any healthier to be consistently fat.

And despite the popular belief that losing weight quickly is tied to yo-yo dieting, a 2016 study found that rapid weight loss did not lead to more weight regain than the slow and steady weight loss people preach.1425

Maybe you’d like to lose weight quickly. We are a world of very heavy people, and the thought of losing 50 pounds by losing a pound a week for a full year—the glacial pace recommended by most authority figures—may seem unbearably slow.

I don’t recommend rapid weight loss for everyone. But everyone should at least understand that the option to lose weight quickly exists, and is generally well-tolerated. If you’re highly motivated to change your life, you shouldn’t let the “pound a week” dogma bore you into staying overweight.

There’s nothing wrong with solving a problem fast.


You’ll lose weight quickly if you eat a lot less. The concerns people have about eating a lot less—potential health complications, losing muscle, and entering “starvation mode”—are greatly exaggerated.



1408. Frayn, Keith. Metabolic Regulation: A Human Perspective. Oxford: Wiley Blackwell. 2010. Print. 9.2.2, page 237.

1409. Stewart, W., and Fleming, L., “Features of a Successful Therapeutic Fast of 382 Day’s Duration,” Postgraduate Medical Journal 49 (1973): 203-209.

1410. Kerndt et al., “Fasting: The History, Pathophysiology, and Complications,” The Western Journal of Medicine 137, no. 5 (1982): 379-399.

1411. Gilliland, I., “Total Fasting in the Treatment of Obesity,” Postgraduate Medical Journal 507, no. 44 (1968): 58-61.

1412. Al-Arouj et al., “Recommendations for Management of Diabetes During Ramadan: Update 2010,” Diabetes Care 33, no. 8 (2010): 1895-1902.

1413. Cahill, G., “President’s Address. Starvation,” Transactions of the American Clinical and Climatological Association 94 (1983): 1-21.

1414. Ibid.

1415. Chaston et al., “Changes in Fat-Free Mass During Significant Weight Loss: A Systematic Review,” International Journal of Obesity 31 (2007): 743-750.

1416. Berg, J., Tymoczko, J., and Stryer, L. Biochemistry. 5th edition. New York: WH Freeman. 2002. 30.3.1.

1417. Heilbronn et al., “Alternate-Day Fasting in Nonobese Subjects: Effects on Body Weight, Body Composition, and Energy Metabolism,” American Journal of Clinical Nutrition 81, no. 1 (2005): 69-73.

1418. Webber, J., and McDonald, I., “The Cardiovascular, Metabolic and Hormonal Changes Accompanying Acute Starvation in Men and Women,” British Journal of Nutrition 71 (1994): 437-447.

1419. Zauner et al., “Resting Energy Expenditure in Short-Term Starvation Is Increased as a Result of an Increase in Serum Norephinephrine,” American Journal of Clinical Nutrition 71, no. 6 (2000):1511-1515.

1420. Mansell et al., “Enhanced Thermogenic Response to Epinephrine after 48-H Starvation in Humans,” American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 258, no. 1 (1990): R87-R93.

1421. Benedict et al. A Study of Prolonged Fasting. No. 203, Carnegie Institute of Washington. 1915. Google Books: Digital Edition.

1422. Major et al., “Clinical Significance of Adaptive Thermogenesis,” International Journal of Obesity 31 (2007): 204-212.

1423. Rosenbaum et al., “Long-Term Persistence of Adaptive Thermogenesis in Subjects Who Have Maintained a Reduced Body Weight,” American Journal of Clinical Nutrition 88, no. 4 (2008): 906-912.

1424. Mehta et al., “Impact of Weight Cycling on Risk of Morbidity and Mortality,” Obesity Reviews 15, no. 11 (2014): 870-881.

1425. Vink et al., “The Effect of Rate of Weight Loss on Long-Term Weight Regain in Adults with Overweight and Obesity,” Obesity 24, no. 2 (2016): 321-327.

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