This Is What Happens to Your Body When You Lose Weight Too Fast

If you’re trying to lose weight, don’t attempt to do so too quickly. Dangerous weight loss methods that promise to help you shed pounds quickly aren’t good for your health. Here’s what your body goes through when you take weight loss too far.

You’ll burn fewer calories

People working out at a gym's treadmill section.

Calorie restriction is not a long-term weight loss solution. | Monkeybusinessimages/iStock/Getty Images

Metabolic rate, your body’s way of regulating a number of biological processes, is largely out of your control. Though it’s nearly impossible to speed up your metabolism over the long-term, many common dieting strategies could end up slowing it down pretty easily.

Intentionally restricting calories, for example, often prompts your body to burn fewer calories in an attempt to store as much emergency energy as possible.

Your hormones might convince you to overeat

A couple enjoys an outdoor lunch.

Extreme workouts and starvation will lead to overeating. |

A hormone in your body called leptin exists to regulate your energy balance. It’s supposed to prevent you from overeating, telling your brain you’re full. According to Healthline, rapid weight loss disturbs this process.

When you burn more calories than you consume, and lose weight too quickly as a result, your body produces fewer leptin hormones. Insufficient levels could increase your appetite, prompting you to eat more — making weight loss nearly impossible.

Your hair and nails will suffer

Cutting nails using nail clipper.

Your nails and hair will suffer if you deprive yourself of a healthy number of calories. | MichalLudwiczak/iStock/Getty Images

The foods you eat every day contain vitamins and minerals that help keep you alive and healthy. If you’re trying to lose weight faster than a doctor would recommend, it’s likely you won’t be able to consume enough of these nutrients — and that could affect your appearance.

According to, deficiencies in one or more B-vitamins, though rare, could affect the growth and strength of your hair and nails. Losing weight could also impact the health of your skin if you aren’t getting enough nutrition or drinking enough fluids.

You’ll destroy your immune system

A woman sneezes into a tissue.

Don’t put your body through too much pressure. | Sam Edwards/OJO Images/Getty Images

When you don’t eat right — even when you’re trying to eat healthier to lose weight — possible deficiencies could hurt your immune system. According to the Academy of Nutrition and Dietetics, nutrients like zinc and vitamin E play vital roles in helping your body fight off infections.

Your focus on fitness could also affect your immunity. You’re more likely to fall prey to bacteria and viruses when you’re exercising too much.

You might lose muscle

A woman workouts at a gym.

Fatigue will weaken your muscles. | Boggy22/iStock/Getty Images

When your body’s desperate for fuel, it can begin to pull energy from your muscles, warns WebMD. Losing muscle mass could have serious side effects, especially since your heart — one of the most important organs in your body — happens to be a muscle.

This is one reason why it’s so important to strengthen your muscles and refuel with protein after a workout when trying to lose weight. This doesn’t make a difference, however, if you aren’t putting enough calories into your body to begin with.

You’ll confuse your brain

A woman works out on a medicine ball.

You’ll notice a loss of focus. | Funduck/ iStock/Getty Images Plus

Losing weight too quickly can affect your blood sugar levels, causing them to drop too low for your brain to handle. According to the Department of Neurology at Harvard, your brain uses sugar as its main fuel source. Half the energy your body produces from sugar goes to your brain.

If you’re not consuming enough carbohydrates — one of the first things many people try to cut from their diets to lose weight — you might find concentrating and taking in information more difficult. “Brain fog” is a telltale sign you’re not putting enough energy into your body.

How to lose weight safely

Woman doing lunges in a gym.

Be patient, and watch the weight come off. |

You don’t have to lose weight quickly to make it happen. Mayo Clinic recommends losing anywhere from one to two pounds per week at most to stay healthy. When you’re first starting out, you might lose a little more because of water weight. But don’t get discouraged if your weight loss slows down.

Reducing your daily calorie intake by 250 — and making sure to burn an extra 250 calories every day — is one way to slowly jumpstart your journey.

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