Why Rapid Weight Loss Can Be Unhealthy for Your Body

When starting a weight loss plan, it's understandable to want to see fast results and aim for something like losing 15 pounds in a month. However, it's important to lose weight at a safe and sustainable pace.

There are risks to rapid weight loss, and losing weight takes time. Taking things slow and steady helps protect your health and ensures that your weight loss results have staying power.

​Read more:​ 5 Weight-Loss Mistakes That Have Nothing to Do With Food

For many people, losing 15 pounds in a month could be achieved through dangerous habits, like extreme calorie restriction or severely limiting what you eat.

"Unsupervised and particularly extreme measures such as starvation, prolonged fasting or stringent food restrictions such as eating only one thing for 30 days can be taxing on the body and may result in electrolyte imbalance, nutrient deficiencies and other unhealthy outcomes," says Jada Moore-Ruffin, MD, a primary care physician specializing in obesity medicine and medical director of REAL Weight Loss + Wellness in Atlanta.

There's also the fact that losing 15 pounds in a month makes it more likely that you'll ultimately gain the weight back in the end. According to the Mayo Clinic, it takes an exceptional amount of effort to lose lots of weight fast, and those changes often aren't sustainable. Extreme changes that interrupt your normal routine can be difficult to implement as long-term habits, so you'll likely have trouble maintaining your results.

For most people, a healthy weight loss goal is about 1-2 pounds per week, according to the U.S. Centers for Disease Control and Prevention (CDC). Plus, those who lose weight gradually are more successful at keeping weight off, according to the CDC. Weight loss involves making long-term lifestyle changes, and with healthy food choices and regular exercise, this type of gradual weight loss is more sustainable in the long run to help you hit your goal weight and maintain it.

There are a few select situations where you can lose 15 pounds in a month safely, or at least without raising much concern from your health care providers. One factor is a very high starting weight.

"If you [have obesity,] losing that much weight at the beginning of a weight loss journey isn't unexpected," says Susan L. Besser, MD, a family medicine physician at Mercy Medical Center in Baltimore.

Another route to losing 15 pounds a month safely is to do so under a medically supervised weight loss program, in which a doctor works closely with you every step of the way. "Intentional rapid weight loss may be facilitated in a healthy way under medical supervision," says Dr. Moore-Ruffin. "There are medications that can be used to stimulate the metabolism and reduce the appetite."

When a doctor is directing your weight loss and supervising your care, it can be safe to lose the weight faster. You could lose up to 20 pounds monthly if done under a medically supervised weight loss program, says Luiza Petre, MD, a board certified cardiologist and weight management specialist in New York City.

The key, Dr. Petre says, is to understand what kind of weight you're losing. "When it comes to losing weight safely, it boils down to making sure we don't lose muscle mass or just water and we lose fat," Dr. Petre says. "Every 3 pounds of fat holds 1 pound of water, so losing 15 pounds a month is feasible and safe if done with the proper nutrition and enough protein intake to protect against muscle mass loss and nutrients and vitamins deficiencies."

Medical weight loss programs are usually geared toward patients with quite a bit of weight to lose or with health issues who require extra observation. By design, they can't be undertaken without the supervision of medical professionals. It's important to have a health care provider monitor your well-being throughout the process.

​Read more:​ Done Losing Weight? Here's How to Maintain Your Hard Work