Whether you want to slim down for a big event (hello, wedding) or to quickly fit into your old jeans, the desire for fast weight loss is understandable. While fad diets can be tempting with wild promises (like, lose 20 pounds in one month!), they also tend to backfire and can wreak havoc on your metabolism. Most dieters who follow strict diets rebound and regain the weight.

Safe and sustainable weight loss, on the other hand, involves a lifestyle change and takes time: “Most of the research supports losing weight at a slow-and-steady pace to maintain the weight loss in the long-term,” confirms Ryan Maciel, RD, a certified strength and conditioning specialist based in Cambridge, Massachusetts.

Still, if you’re wondering exactly how much weight you can safely lose in one month, here’s your guide, according to weight-loss experts:


Weight loss depends on a myriad of factors, like age, gender, physical activity level and the effects of certain medications, so everyone goes at their own pace. A good rule of thumb is to aim to lose 1–2 pounds per week or 4–8 pounds per month, says Dr. Elizabeth Lowden, a bariatric endocrinologist at Northwestern Medicine Metabolic Health and Surgical Weight Loss Center at Delnor Hospital in Chicago. In other words, that’s about 5–10% of your body weight.

If you want to lose a pound a week, you’ll need a calorie deficit (aka less calories in comparison to those you need to maintain your current weight) of about 3,500 calories, or 500 calories per day, explains Lowden. Because it can be difficult to decrease your intake by that much, upping your physical activity can help burn more calories.

Keep in mind, though, week 1 of your weight-loss plan may be misleading. “It wouldn’t be uncommon to lose 5 pounds your first week, maybe even up to 10, but this isn’t a rate you can expect to continue — and you may even notice no weight loss the next couple of weeks,” says Lowden. That’s because as you lower your caloric intake and begin making healthier eating choices, your glycogen stores (aka molecules made from the carbs you eat) drop, and since they’re attached to water molecules, you lose water weight with them, explains Lowden. “So don’t feel discouraged if you initially burn pounds fast then fall into a weight-loss slow down — this is normal.”


“Unless you’re enrolled in a medically-supervised weight-loss program or you’ve just had bariatric surgery, it’s very uncommon to lose more than 10 pounds per month,” says Lowden. Remember, if you lose weight too quickly, your body fights back. Your metabolism slows down, your hormones shift to increase your cravings and appetite, and you even burn less fat, according to a review in the International Journal of ObesityThese changes could lead to disordered eating habits, warns Lowden.

What’s more, no matter how quickly you’re losing weight, you also lose a certain amount of lean muscle mass in the process (especially if you’re not working out to build muscle), and losing too much could deeply damage your metabolism. That’s why strength training when trying to lose weight is important. Plus, a diet too low in calories could result in nutritional deficiencies, and rapid weight loss could lead to gallstones from improper gallbladder functioning, adds Maciel.

In short, a speedy weight-loss regimen to drop a dress or pants size is generally not worth it. As frustrating as it may be, try to be patient so you are successful long-term.

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