Weight-loss shakes, also called liquid meal replacements, are calorie-controlled beverages that replace one or more meals or snacks as part of a weight-loss program.
"They have a fixed number of calories, usually 160 to 290 calories per shake, and contain key nutrients found in a healthy meal or snack," says Linda Delahanty, M.S., R.D., chief dietitian and director of nutrition and behavioral research at the Massachusetts General Hospital Diabetes Center. Commonly consumed weight-loss shakes include SlimFast, Medifast, Atkins and HMR.
Weight-loss shakes are used in weight-loss programs because they are portion-controlled and convenient.
"Using weight-loss shakes helps simplify the decisions you need to make about what to eat and can reduce time needed to prepare meals," Delahanty says.
Weight-loss shakes also work—in the short-term. "People who use these portion-controlled foods to replace two meals per day can lose about 50 percent more weight than those who don't," Delahanty says.
This is because the shakes provide fewer calories than what someone would normally consume at a meal. "A caloric deficit, regardless of how it is achieved, can stimulate weight loss, and many individuals find that replacing meals and/or snacks with weight-loss shakes allows them to do that," says Cara Harbstreet, M.S., R.D., L.D., of Street Smart Nutrition.
A 2018 study found that weight-loss shakes might lead to more weight loss than a meal with the same number of calories. When obese individuals replaced all their meals with weight-loss shakes for three weeks, they lost more than twice the amount of weight as obese men and women who consumed the same number of calories but through food. Those who drank the shakes also had reduced food cravings. Weight-loss shakes can also help individuals with type 2 diabetes lose weight.
Jenn LaVardera, M.S., R.D., owner of Hamptons RD, says, "Weight-loss shakes can be beneficial for short-term weight loss because they help with calorie control while providing all the essential nutrients your body needs."
However, while they can be used to help you slim down fast, LaVardera says don't expect to maintain the loss. "Once you are off the shakes, you are likely to return to your old eating habits and gain the weight back," she says.
If you consume weight-loss shakes for the rest of your life, you might be able to sustain your weight loss long-term. The problem is, most people don't live on weight-loss shakes forever. People go back to eating real food as soon as their weight-loss program or diet is over.
"Weight-loss shakes do not offer a long-term solution because they are usually not sustainable for more than a few months," Harbstreet says.
This is because they take the fun and pleasure out of eating, says Kara Lydon, R.D., L.D.N., R.Y.T, intuitive eating counselor and blogger at The Foodie Dietitian. "We often forget that food is meant to be pleasurable; it's what helps us to survive as humans. Imagine if food wasn't pleasurable. We probably wouldn't be as compelled to eat to survive. Over time, people are going to start seeking out pleasure from food again because they aren't going to get it from a weight-loss shake."
Research shows that weight regain is a problem after most, if not all, diet programs. This is due to biological and hormonal responses that increase appetite, alter metabolism and promote weight gain. "One research article that reviewed over 30 studies on dieting concluded that dieting is actually a predictor of weight gain," says Lydon.
This may seem daunting, but it doesn't have to be all-or-nothing. "Using one weight-loss shake per day can help keep off the weight you have lost long-term or be a tool to help refocus on weight loss if you regain some weight over time," Delahanty says.
Weight-loss shakes can be one of many tools in your nutrition toolbox to help you maintain a healthy weight over time. Tracking food intake, weighing regularly and exercising are other tools that have proven effective in helping people keep the weight off long-term.
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Besides not being sustainable long-term, there are other downsides to drinking weight-loss shakes.
"The severe restriction in calories can create unintended side effects, such as suboptimal intake of certain nutrients, slowed metabolism and loss of connection with hunger or satiety signals," Harbstreet says. "The liquid nature of this diet also can remove fiber from one's diet, potentially altering gut health or creating a less-filling eating—or, in this case, drinking—experience." Fiber helps increase satiety and can help with weight management long-term.
Weight-loss shakes can also leave people in a dieting mentality—seeing foods as good or bad and feeling guilt over eating "bad" foods. This often leads to a cycle of restricting food, bingeing and then restricting again. It also doesn't set you up for success in the real world. What do you order if you're eating at a restaurant? What do you eat at a party if you don't have your shake? It makes the transition from weight-loss shakes to solid food difficult.
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Weight-loss shakes lead to weight loss temporarily, but they aren't sustainable long-term. They leave people in a dieting mentality, take the pleasure out of eating and can be expensive. You can maintain a healthy weight long-term by eating real food. Here, tips on making weight loss work without the shakes.
Studies show that high-fiber breakfast cereals can be just as effective for weight loss as weight-loss shakes because the fiber increases satiety. Eating breakfast has also been associated with maintaining weight loss long-term. Fiber is found in whole grains, fruits and vegetables.
LaVardera teaches her clients to make half of their plate vegetables and eat smaller portions of starches and animal proteins. "Vegetables add fiber and water content to help keep you full, and are packed with nutrients. I want my clients to be able to make food decisions in the real world—at the store, at a dinner party, at a work lunch—so they need to know how to choose whole, real foods and not rely on shakes," LaVardera says.
Harbstreet agrees that the best way of eating is one that you can keep up for the long-term.
"What is most important is identifying sustainable behaviors that allow flexibility and adaptation," she says. "Sticking to a rigid or strict diet promotes dieting behaviors and replaces someone's innate sense of trust in their body with an external cue, such as a meal plan, diet or list of approved foods."
Lydon echoes this advice. "Once we let go of the external cues telling us what and how much to eat, we can free up space to tap into the innate wisdom of our own bodies, also known as intuitive eating," Lydon says. "And that is a 'plan' that's sustainable. It's what we were born doing."
Still, some people do better with structure. Check out our weight-loss meal plans for real food with real benefits. Working with a dietitian can help you find the best long-term eating plan for you and your goals. Many health care professionals recommend an 80/20 approach: 80 percent of the time, aim to make your plate half vegetables, one-quarter whole grains and one-quarter healthy protein; the other 20 percent of the time, allow yourself to indulge, but do it mindfully. This eliminates the all-or-nothing dieting mentality and the restrict-binge-restrict cycle that many people fall into when trying to eat healthy 100 percent of the time.
Weight-loss shakes work in the short-term but aren't sustainable long-term. Focus on adding more fiber to your diet through fruits, vegetables and whole grains.