Why is Losing Weight too Fast is Bad?

It's normal if you want to lose weight as fast as possible.

But you've probably been told that it's better to lose weight at a slow, steady pace.

That's because most studies show that people who lose weight slowly are more likely to keep it off long-term. Losing weight slowly also comes with far fewer health risks.

However, several recent studies have found that rapid weight loss might be just as good and safe as slow weight loss.

So is it actually bad for you to lose weight fast? This article digs into the research to uncover the truth.

What Is Considered Fast Weight Loss?

According to many experts, losing 1–2 pounds (0.45–0.9 kg) per week is a healthy and safe rate.

Losing more than that is considered too fast and could put you at risk of many health problems, including muscle loss, gallstones, nutritional deficiencies and a drop in metabolism.

The most common ways that people try to lose weight fast are by exercising a lot, and by following a"crash diet" or a very low-calorie diet of fewer than 800 calories per day.

People often prefer the option of eating a very low-calorie diet, since it is often easier to lose weight through diet than exercise.

However, if you're just starting a diet or exercise plan, then you may lose much more than 2 pounds (0.9 kg) in your first week.

For this initial period, fast weight loss is perfectly normal. The weight you lose during this time is commonly called "water weight."

When you consume fewer calories than your body burns, your body starts dipping into its stores of energy, known as glycogen. The glycogen in your body is bound to water, so when you're burning glycogen for fuel, the body also releases that water.

This is why you might experience a major drop in weight during your first week. Once your body uses up its glycogen stores, your weight loss should stabilize at 1–2 pounds (0.45–0.9 kg) per week.

What Are the Risks of Rapid Weight Loss?

Rapid weight loss creates physical demands on the body. Possible serious risks include:

  1. Gallstones, which occur in 12% to 25% of people losing large amounts of weight over several months
  2. Dehydration, which can be avoided by drinking plenty of fluids
  3. Malnutrition, usually from not eating enough protein for weeks at a time
  4. Electrolyte imbalances, which rarely can be life-threatening

Other side effects of rapid weight loss include:

  • Headaches
  • Irritability
  • Fatigue
  • Dizziness
  • Constipation
  • Menstrual irregularities
  • Hair loss
  • Muscle loss

The dangers of rapid weight loss increase with the time spent on the diet. Eating a no-protein diet is particularly risky.

The Bottom Line

There’s nothing wrong with dropping pounds quickly — as long as you’re doing it smartly. Losing weight more quickly may give you more motivation to keep going, though it doesn’t really matter how many pounds you lose a week. The only thing that matters is the method you’re using to experience weight loss and how well you follow your maintenance plan.


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