Is It Bad to Lose Weight Too Quickly?

Rapid weight loss can harm your health and lead to weight regain
Person in exercise clothes looking at their reflection in a mirror

When you’re ready to slim down, you want to make it happen now. But most health experts say rapid weight loss isn’t the way to go. It can sabotage your long-term weight loss goals and may hurt your health, too.

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Why is it bad to lose weight quickly? Endocrinologist and obesity specialist Marcio Griebeler, MD, explains why slow and steady wins the weight-loss race — and how to do it.

What is rapid weight loss?

There’s no magic number that qualifies as “rapid weight loss.” Your weight, age and activity level determine what that term means for you.

Don’t worry too much about the number of pounds you should (or shouldn’t) lose. Instead, look at the diet plan you’re following to lose weight. Extreme diets with lofty promises usually fall under the “rapid weight loss” category.

“Avoid super restrictive diet plans because they’re difficult — if not impossible — to keep up over the long term,” says Dr. Griebeler. “If the diet plan isn’t something you can stick to for months or years, it’s probably a fast weight loss plan. And those plans and gimmicks aren’t a healthy, sustainable way to lose weight.”

A more moderate goal of losing 1 to 2 pounds per week tends to be more successful over the long haul. 

Risks of fast weight loss

It’s hard to resist the lure of rapid weight loss. Be 10 pounds lighter by next week? Yes, please. But don’t give in to the flashy ads. Most of the time, those diet plans are bad news for your health.

Your metabolism shifts to low gear

Your metabolism is your body’s calorie-burning process. And a metabolism that’s out of whack can damage your body’s ability to keep the weight off.

“When you lose weight too quickly, your body slows down its calorie-burning process,” explains Dr. Griebeler. “That is your body’s way of trying to ensure you don’t starve. You might lose a good amount of weight right away, but your metabolism quickly goes into survival mode.”

The change in your metabolism is a key reason why people regain weight after trying rapid weight loss plans. When you go back to eating a regular diet, your metabolism isn’t used to that many calories — and the pounds come back.

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You lose muscle mass  

When you cut way back on calories, you might see that number on the scale drop like a rock. But it’s not just fat you’re losing. You’re also losing muscle.

“Sudden and severe calorie restriction will make you lose muscle mass as well as fat,” says Dr. Griebeler. “It’s harder to lose weight when you don’t have enough muscle mass because muscles burn lots of calories.”

Slower weight loss combined with exercise, on the other hand, gives your body time to lose fat while keeping your muscle mass. And bonus: You keep your muscles’ calorie-burning power intact.

You miss out on important nutrients

Your body needs a certain amount of fat, protein and carbs to function. It also needs a whole range of vitamins and minerals. When you slash calories or cut out entire food groups like carbs or dairy, you risk:

“There’s nothing wrong with cutting calories if you’re eating a variety of nutrient-rich foods,” says Dr. Griebeler. “Your diet should contain a wide variety of healthy, whole foods. Don’t try to cut more than 500 calories a day.”

You’ll likely quit your diet

When you go for fast weight loss, you may find that it gets harder — not easier — to keep losing weight. A couple of weeks in, you’ll likely feel famished all the time. The temptation to crawl into bed with a box of cookies is real.

Don’t blame a lack of willpower. It’s your hormones, and they’re doing exactly what they were designed to do.

“Cutting too many calories too quickly triggers hormonal changes that make you want to eat,” says Dr. Griebeler. “Even a very determined person will find it difficult to overpower those hunger hormones. These fast hormonal changes make you so hungry that they set you up for diet failure.”

Healthy (and steady) weight loss should be your goal

There’s no single diet that works for everyone. But these general guidelines can help you lose weight — and keep it off — in a healthy way.

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Build muscle while you lose weight

Healthy weight loss isn’t just about what you eat. You need physical activity if you want maximum results.

Cardiovascular exercise like walking burns calories, but strength training is just as important. When you lift weights or do resistance training, you increase muscle mass. And when you have more muscle mass, you:

  • Burn more calories, even at rest.
  • Improve your balance and reduce your risk of falls.
  • Reduce joint pain and symptoms of arthritis so you can keep moving and losing weight.
  • Strengthen your bones and reduce your risk of fractures and osteoporosis. 

Make sleep a priority

Ever notice that when you’re exhausted you want to eat more? When you’re tired, your hunger hormones barge in and ruin your chances of bypassing that donut. If you’re regularly missing out on sleep, even the best weight loss plan is going to feel impossible.

“Aim for at least seven hours of quality sleep each night,” says Dr. Griebeler. “If you consistently have trouble sleeping, talk to your doctor. Many people who have sleep disorders don’t know it — and sleep disorders are treatable.”

Find a balance

Think about your diet plan and whether you could do it for the rest of your life. Cutting a couple of hundred calories a day? Doable. Never having a bowl of ice cream again? Probably not.

“The best diet is one you will stick to,” says Dr. Griebeler. “Changing our habits is hard, but it can be done. Choose a diet plan that allows you to have an occasional piece of chocolate or slice of pizza. It’s much easier to keep doing these types of plans for months and even years.”  

Fast results are fun for a while, instant gratification isn’t best when it comes to weight loss. Go slow with dropping pounds so you can be healthier today and stay that way for years to come.

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