Is Losing Weight Fast Dangerous?

A reader emailed me the other day: “Is rapid weight loss dangerous?”

This is actually a fairly common question. And when I see it, here’s what I read between the lines: “How bad would it be if I starved myself to drop a few pounds?”

The answer: Pretty bad. Not because it’s unhealthy—though it can be—but because in the long run this strategy will make you fat. Really.

When it comes to losing weight, how fast is too fast? We asked Men’s Health Weight Loss Coach Alan Aragon, M.S., a nutritionist who works with Olympic and professional athletes, for his perspective. His definition: “Dropping pounds so rapidly that in addition to losing fat, you lose muscle too. This isn’t ‘dangerous’ as in ‘life-threatening,’ but it’s not good for your overall health.”

Here's why: Losing muscle reduces your ability to burn calories and regulate your blood sugar, says Aragon—and, of course, it makes you weaker. (To keep your calorie-burn high, use our 100 greatest fitness tips of all time.) What’s more, lost muscle is often replaced by fat when you stop dieting. The result: You end up looking flabbier than ever. After all, each pound of fat takes up 18 percent more space on your body than each pound of muscle.

Aragon dug into the scientific research to determine the rate that different people could lose weight without losing muscle. His findings:

* Obese to morbidly obese: 3 to 5 pounds per week
* Overweight: 2 to 3 pounds per week
* Lean to average: 1 to 2 pounds per week
* Very Lean: 0.5 to 1 pound per week

AMERICA'S FITTEST FEMALE ATHLETES: We found them and ranked them! See if you agree.

Of course, you can help your cause even more by lifting weights while you diet. Research shows that this can prevent the wasting of muscle, helping ensure your weight loss is pure fat.

The other dangers of rapid weight loss: bone loss, dehydration, and an increased risk of binge eating in some people. “But these are typically the result of severe caloric restriction,” says Aragon. His solution: “I’ve found that you can use a simple formula to calculate a smart and effective caloric intake; it’s based on your target body weight.”

For example, let’s say you’re a man who weighs 220 pounds, but you’d like to tip the scales at 180 pounds. You’ll base your calorie intake on that of a 180-pound guy. Now if you don’t do any resistance exercise (you should!), simply multiply your target body by 11. That’s the minimum number of daily calories you should consume for healthy weight loss, with little risk to your muscles.

If you do lift weights, use 9—instead of 11—and add to that the number of hours you work out per week. So if you exercise one hour a week, you’ll multiply your target body weight by 10. If you exercise two hours a week, you’ll multiply your target body weight by 11; if you exercise three hours a week, you’ll multiply your target body weight by 12; and so on. (The extra activity will allow you to eat more and still lose just as fast.)

Then remember these tips as you start your weight loss program:

1. Prepare to plateau. “Your weight drop will be linear at first, meaning you’ll typically lose a steady amount every week,” says Aragon. “However, as you get lighter, your weight will tend to drop in a stepwise manner. So don’t get discouraged if scale holds for a few days, or even a couple of weeks. The closer you get to your goal, the longer the stalls or plateaus can be.”

2. Take a time out. Every 8 to 12 weeks, take 7 days completely off from dieting. “Don't consciously try to stuff your face, but don't rigidly restrict yourself either,” says Aragon. “This is a good mental and physical break from dieting that allows people to sustain their diets for longer periods.”

3. Redefine progress. “Look at other determinants of success besides the scale,” says Lisa Sasson, R.D., associate professor of nutrition at New York University. Monitor your triglycerides, blood pressure, and body fat percentage. As these numbers improve, you’ll have even more motivation to stick with your eating plan.

Remember the Men's Health mantra: If you have a problem, we have your solution. Click here for news and advice that can improve your life everyday!

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