Health Debunked: Can You Safely Lose Weight Quickly?
Key takeaways:
A sustainable approach to weight loss should help you lose a maximum of 2 lbs per week.
Losing weight rapidly means you’re likely losing water and muscle and will probably regain the weight quickly.
Weight-loss diets that produce fast results are often very low in calories and can cause issues such as nutrient deficiencies.
There are many fad diets that promise a quick fix for weight loss. Perhaps you’ve seen the ads featuring people who lost a lot of weight or dropped a few pant sizes in just 10 days. But is this type of quick weight loss realistic? And is it safe for your overall health?
What is fast weight loss?
A realistic weight-loss goal is losing a maximum of 2 lbs per week, according to the CDC. At this pace, you may learn habits grounded in nutritious eating and healthy exercise. And you may start to add smart, sustainable changes to your lifestyle.
You’re more likely to stay at a weight that feels right for you if you make lifestyle changes rather than trying a fad diet.
Save every month on GLP-1 meds with GoodRx
Save an average of $235 on FDA-approved GLP-1s like Ozempic and Zepbound.
Fast weight loss is different. It’s common for fad diets to promise accelerated weight loss of up to 10 lbs or 15 lbs per week. These fast-fix diets are often accompanied by:
Very low-calorie eating plans
Diet pills
Weight-loss drinks
Fasting regimes
Diets like these can fall short of essential nutrients and don’t teach long-term, sustainable, healthy habits.
Claim: Losing weight fast can be healthy
Many fad diets claim that they can deliver fast weight loss. Some of these diets are very low in calories (less than 800 calories per day). And some recommend pills or weight-loss drinks that promote water loss through frequent urination or diarrhea.
So, are these a healthy choice when it comes to making sustainable weight changes?
What does the science say about losing weight quickly?
Fast weight-loss diets aim to reduce calorie intake and to burn more calories. Eating less and moving more can affect your weight. But it’s not the whole picture. Your weight is also related to many other factors, including:
Food accessibility and affordability
Medical conditions
Hormone levels
Medications
Cooking skills
Level of education
Crash diets and health: Learn about the health risks of rapid weight loss with crash dieting.
Weight-loss strategies: Managing your stress and getting more sleep can help you reach your weight goal. We review 12 science-backed strategies to lower your weight.
A personal story of weight loss: Read how Shawn used both mindset and medication to help him on his weight-loss journey.
Eating less and moving more is still the only thing that many clinical diet studies focus on. Fast weight-loss plans may “work” in the short term, since they can help you lose weight. But the pounds that you drop are mostly from water and muscle, rather than fat. True weight loss involves shrinking fat cells, not just eliminating water for a temporary fix.
Fast vs. slow weight loss
One study looked at fast weight loss versus slow weight loss. In the study, fast weight loss was considered 5% weight loss in 5 weeks. And slow weight loss was 5% weight loss in 15 weeks.
Both approaches led to lost pounds. But with slow weight loss, people lost more fat and less muscle. So the changes in their body composition was more favorable. Both fast and slow weight loss improved lipid and blood sugar levels.
However, the study didn’t evaluate what happened long term, and that’s a major problem. Studies show that fast weight loss is usually temporary. And weight regain is common.
Plus, if you follow a diet of eating less and moving more, your body will make adjustments, like to your metabolism and hormone levels. These changes are your body’s way of resisting weight loss. So the fast weight-loss diet won’t lead to real results in the end.
Low-calorie diets
Low-calorie diets with less than 800 calories a day aren’t recommended, except in limited circumstances, such as before surgery. Eating such a small amount of food can result in:
Nutrient deficiencies
Supplements for weight loss
Some supplements are promoted for fast weight loss, such as caffeine or green tea extract. These can be labeled as “fat burners.” And they’re said to increase weight loss by increasing your fat metabolism.
However, there’s not enough evidence on these supplements to make these claims. So, don’t trust the marketing saying otherwise.
What do the experts say about slow vs. rapid weight loss?
“Quick weight loss results in water and muscle loss, not true fat loss,” explained dietitian Lisa Andrews, who works at Soundbites Nutrition in Cincinnati, Ohio.
Andrews explained that cutting calories too much by dramatically reducing your food intake may lead to electrolyte abnormalities. And the reduction in muscle mass can negatively impact metabolism in the long term.
“Slow and steady weight loss is much healthier and easier on the body long term,” said Andrews.
Hormone changes
Meanwhile, fast weight loss can negatively impact the hormones that are involved in appetite and body weight, including leptin and ghrelin, said dietitian Michele Phulsuksombati of Food Frame of Mind in Frederick, Maryland.
“In theory, leptin suppresses appetite, and ghrelin increases appetite,” said Phulsuksombati. “If you lose 10 lbs in a week, the body thinks it needs to eat, as the leptin levels are low and ghrelin levels rise.”
This can cause weight gain, rather than weight loss.
Muscle loss, medical problems
“Weight loss is not a race,” added dietitian Melissa Mitri of Zen Master Wellness. “When you lose weight too quickly, it puts you at risk for muscle loss, nutrient deficiencies, and medical problems such as gallstones. It can actually slow your metabolism over time.”
How can I healthily lose weight?
Weight loss is complicated and different for everyone. And finding a comfortable body weight for you depends on your personal goals. But there are some general tips you can lean on to lose weight in a healthy way.
The Academy of Nutrition and Dietetics recommends lifestyle intervention, which includes:
Eating nutritious foods
Moving more
Addressing eating behaviors
Building a healthy sleep routine
Work with a dietitian or healthcare professional to figure out an eating and moving plan that works for your needs. This plan should be sustainable, enjoyable, and accessible — as well as affordable. For more information on weight loss, check out our guide here.
Frequently asked questions
Losing weight too quickly can be harmful for your health. Crash diets can lead to:
Poor nutrition
Hormonal changes
Mood problems
Disordered eating
Gallstones
These diets can also make you gain more weight in the long term. That’s because when you drop weight quickly, you’re more likely to gain back the weight you lost.
Some people believe that apple cider vinegar can help you drop weight quickly. One small study showed that people who drank apple cider vinegar daily for 12 weeks lost more weight, especially in their waist area. But larger studies are lacking. Overall, there isn’t good evidence that apple cider vinegar helps with weight loss.
The 30 30 30 rule is a weight loss trend that became popular on social media. It involves:
Eating breakfast within 30 minutes of waking up
Eating 30 g of protein at breakfast
Getting 30 minutes of exercise after breakfast, with steady, low-intensity exercise
Studies suggest that people who eat a high-protein breakfast are less hungry and eat fewer categories later in the day. But there aren’t studies looking at this particular diet, so there’s no evidence that it will help you lose weight quickly.
The bottom line
If you’re interested in sustainably losing weight, skip the fad diets and unregulated supplements. They may offer a quick solution, but ultimately they can be dangerous and unsustainable.
And remember: Your weight doesn’t define you. Healthy lifestyle habits are more important than the number on the scale. But if you’re interested in healthily losing weight, do so slowly, and reach out to a healthcare professional for help.
Why trust our experts?
References
Ashtray-Larky, D., et al. (2017). Rapid weight loss vs. slow weight loss: Which is more effective on body composition and metabolic risk factors? International Journal of Endocrinology and Metabolism.
Centers for Disease Control and Prevention. (2023). Steps for losing weight.
Constable, P. D., et al. (2017). Disturbances of free water, electrolytes, acid-base balance, and oncotic pressure. Veterinary Medicine.
Erlinger, S. (2000). Gallstones in obesity and weight loss. European Journal of Gastroenterology and Hepatology.
Ferraro, Z. M., et al. (2015). Unhealthy weight control practices: Culprits and clinical recommendations. Clinical Medicine Insights: Endocrinology and Diabetes.
Fothergill, E., et al. (2017). Persistent metabolic adaptation 6 years after The Biggest Loser competition. Obesity.
Hasani-Ranjbar, S., et al. (2009). A systematic review of the efficacy and safety of herbal medicines used in the treatment of obesity. World Journal of Gastroenterology.
Khezri, S. S., et al. (2018). Beneficial effects of apple cider vinegar on weight management, Visceral Adiposity Index and lipid profile in overweight or obese subjects receiving restricted calorie diet: A randomized clinical trial. Journal of Functional Foods.
Kim, J. Y. (2020). Optimal diet strategies for weight loss and weight loss maintenance. Journal of Obesity and Metabolic Syndrome.
Launholt, T. L., et al. (2020). Safety and side effects of apple vinegar intake and its effect on metabolic parameters and body weight: A systematic review. European Journal of Nutrition.
Mendoza-Herrera, K., et al. (2021). The leptin system and diet: A mini review of the current evidence. Frontiers in Endocrinology.
Nadolsky, K. (2020). Fad diets explained. American Association of Clinical Endocrinology.
National Institutes of Diabetes and Digestive and Kidney Diseases. (2017). Dieting and gallstones.
Qiu, M., et al. (2021). Effect of protein-rich breakfast on subsequent energy intake and subjective appetite in children and adolescents: Systematic review and meta–analysis of randomized controlled trials. Nutrients.
Raynor, H. A., et al. (2016). Position of the Academy of Nutrition and Dietetics: Interventions for the treatment of overweight and obesity in adults. Journal of the Academy of Nutrition and Dietetics.
Seo, M. H., et al. (2019). 2018 Korean Society for the Study of Obesity guideline for the management of obesity in Korea. Journal of Obesity and Metabolic Syndrome.
