Whether you have a dress you want to fit into for an important party or just want to improve your health, it’s not uncommon to set small weight loss objectives in the hopes of eventually achieving a bigger goal. But people often set their sights on a number far too lofty, which, unfortunately, can lead to failure. Or worse, even to bigger health issues down the line. So how much weight is safe to lose in a week?
Our experts weigh in on how much weight is actually healthy to try to lose in a week.
How exactly happens to your body when you start losing weight?
Our understanding of the science behind weight loss is changing for the better, according to Cyrus Khambatta, PhD, an expert in insulin resistance and weight loss and co-founder of Mastering Diabetes.
“For many years, the weight loss industry has been plagued by promises of rapid weight loss in short periods of time, brainwashing people into believing that rapid weight loss is (a) possible (b) safe and (c) normal,” Khambatta says.
But sustainable weight loss is far more complex—in large part because reducing body fat is more than just a number on a scale.
When you start a new weight loss regimen, your hope is always to reduce body fat. But fat isn’t the only thing contributing to weight loss or gains. Water and muscle can both contribute to a rising or falling number on the scale, and as a result, your weight can actually fluctuate several pounds in a given week—or even in a given day—without actually reflecting true fat loss.
“People want to lose fat and not be fooled by losing water weight,” says Robert S. Herbst, powerlifter, personal trainer, and weight loss and wellness expert. “We are constantly losing water through respiration (breathing), perspiration, and urination. Water weight loss is temporary and will be regained as soon as the person drinks water.”
Rapid weight loss, at least at the beginning of a regimen that you might notice when you start making these lifestyle changes, is frequently actually water, not fat, especially if one is opting for a low-carb diet to lose weight. Because the body stores carbohydrates as glycogen for quick energy, and each gram of pure glycogen binds three or four grams of water, burning glycogen—which happens as part of any weight loss protocol, but especially with a low-carb regimen—leads to quick weight loss, at least at the start.
“You can burn through the majority of your glycogen reserve within approximately 24 hours,” says Khambatta. “It is not a very large storage tank of energy. As you lose glycogen, you also lose three times as much water, resulting in rapid weight loss in the initial phase of a weight-loss program.”
To monitor your true weight loss, try to always weigh yourself at the same time of day: first thing in the morning after going to the bathroom.
“If that morning weight goes down over time, they will be losing fat,” says Herbst.
How much weight is safe to lose in a week?
Most experts, including the CDC and Academy of Nutrition and Dietetics, agree that a loss of between one and two pounds of fat per week is an appropriate, healthy benchmark to shoot for.
That may sound like a lot, but never fear. Choosing nutrient-dense foods that keep you full such as produce, lean meats, and healthy fats will help make this transition easier. And as Keith-Thomas Ayoob, EdD, RD, FAND, Associate Clinical Professor Emeritus at the Albert Einstein College of Medicine says, “The deficit doesn’t have to come from diet alone.”
“Some exercise to burn some of those 500 or 1,000 calories will help you lose as well and can take some of the burden from the dietary intake,” he says.
There are, nevertheless, a few exceptions to this rule—notably people who have more to lose.
“Just like when a bodybuilder lifts weights at the gym, an overweight person lifts their body weight as they move through their day,” says Becky Gillaspy of Dr. Becky Fitness.com. “As you lose weight, there is less of a strain on your muscles, so you do not expend as many calories as you [do] near your goal weight.”
What are the dangers of losing weight too quickly?
Some people are tempted to cut back further—or over-exercise—in an attempt to lose weight even faster. Our experts discourage this vehemently, as it can lead you to lose lean muscle, slow your metabolism, miss out on key nutrients, or you could even develop gallstones, which can form from breakdown products that are not excreted.
Losing weight at a slower rate also ensures you’re doing so sustainably, and you’ll be far more likely to keep the weight off in the future.
“Slow weight loss gives the person time to adapt to new healthy lifestyle changes,” says Summer Yule, MS, RDN. “They may be more likely to sustain the loss if they do not treat it as a quick-fix diet and instead modify their diet and physical activity pattern in a way that they can sustain for life.”
Tracy Rodriguez, NASM certified personal trainer, agrees.
“Rapid weight loss with too large of caloric deficit can slow down your metabolism, meaning that it will be challenging to keep the weight off,” she says. “If you lose weight too quickly, it will fight to get back to the weight it’s used to. If you lose weight slowly and steadily, it will fight to keep you at your new weight.”
Ultimately, however, setting additional goals unrelated to the number of pounds lost is the best way to encourage sustainable weight loss.
“Every person differs on how quickly they can lose weight safely,” she says. “A number is just a number. It should be about fitness and health, not a number.”
And this, frankly, is the best course of action.
“Setting other goals like fitting into an old pair of jeans, or developing more muscle definition, is oftentimes more helpful,” says Jennifer Fiddler, M.A., CPPC. “In general, a combination of outcome goals (I want to weigh [a certain number of pounds], I want to be able to do [a certain number of] push-ups, etc) and process goals (I will hit the gym three times a week, I will drink 60 ounces of water a day) usually is the best way to keep somebody motivated and provide little wins along the way.”