Weight Loss & Diet

How to lose weight: Weight loss tips backed by science

You might be tempted to lose weight fast, but is that the best way?

It’s hard to resist the allure of quick fixes—especially when it comes to weight loss. But diet plans and weight loss programs that promise rapid or immediate results aren’t always sustainable. What’s more, they could take a serious toll on your physical and mental wellbeing. To suss out the difference between weight loss spread over days versus weeks or months and the effects of each, read on:

How fast should you lose weight?

"Losing one to two pounds per week constitutes healthy weight loss,” says Brooklyn-based dietitian Brocha Soloff, RD, CPT. “More than that is too fast, especially for women, who tend to lose weight slower than men thanks to a combination of hormones, fat distribution, and comparatively slower metabolisms.” 

According to the Centers for Disease Control and Prevention, pounds taken off gradually are more likely to stay off than pounds shed rapidly. When you drop weight too quickly, you not only risk regaining most, if not more, of it; you increase your risk of certain health complications.

For instance, rapid weight loss can trigger headaches, fatigue, irritability, and constipation, says registered dietitian and strength coach Ben Tzeel, RD, CSCS. Mental fogginess, difficulty concentrating, dizziness, and hormone irregularities can also occur, he adds, blaming low blood sugar, dehydration, electrolyte imbalances, and hunger hormones that may bubble up in response to an abrupt reduction of nutritional intake. More than a few weeks of intense caloric deprivation can also cause muscle loss, hair loss, gallstones, and menstrual irregularities in women that can increase the risk of osteoporosis, says Tzeel.

Given the potential for side effects, it’s important to understand exactly how potentially hazardous weight loss diets differ from sustainable weight loss solutions.

Understanding the science behind weight loss

Generally, eating fewer calories than your body burns leads to the loss of body weight, which is typically comprised of water weight or body fat. But factors unrelated to caloric intake can influence the pace at which your body burns calories: 

How diet impacts weight loss

Because some foods (like most forms of protein) require more energy to metabolize than others (say, carbohydrates), digesting them may burn more calories than other foods, Tzeel says. However, on extremely low-calorie diets, deprivation causes your body to shift into self-preservation mode: To compensate for the lack of incoming energy, your metabolism may slow down—which makes fat loss more difficult.

Different eating approaches can lead to different types of weight loss: Diets that elicit rapid weight loss (think: ones that recommend eating only one or two foods, like the cottage cheese or cabbage soup diet, or the extremely low-carb keto diet) primarily encourage the rapid loss of water weight, Soloff says. That’s because a sudden restriction of calories (especially carbs) depletes the body of glucose, it’s most easily accessible source of fuel, forcing the body to tap stores of glycogen—a compound that’s comprised of more water molecules than glucose, Soloff explains. Those water molecules get lopped off and excreted in urine when glycogen is broken down for fuel. What’s more, most rapid weight loss diets scrap foods that promote water retention, like high-sodium options. This causes further loss of water weight through urine, which contributes to weight loss.

Gradual weight loss usually involves more fat loss because fat is a last resort as a fuel source. The body typically needs to deplete glycogen stores before it opts to break down fat for fuel, Soloff adds—in large part, because converting fat to usable energy requires more effort than breaking down glucose and glycogen.

The benefits you derive from any amount of weight loss depend on your ability to keep that weight off, Soloff says. Repeatedly losing and regaining weight—which is more likely when going on and off of extreme diets—can increase your cardiovascular disease risk, chip away at your psychological wellbeing, and may make sustained weight loss harder. 

What metabolism has to do with weight loss

The pace of your metabolism determines how quickly your body turns the food you eat into energy. People with more muscle mass tend to have faster metabolisms. (This is why men, who tend to have more muscle mass than women, also tend to have faster metabolisms and why you may experience weight gain as you age and lose muscle mass.) Restricting calories can also cause your body to break down muscle for fuel and thus slow down your metabolism.

How your starting weight affects weight loss

A low body weight can mean a slower metabolism, according to Soloff, since moving a smaller body around requires less energy than moving around a larger one. Unfortunately, this means that the more weight you lose, the harder it is to sustain weight loss or lose more weight. 

How your hormones affect weight loss

Certain hormones also affect how easily you lose weight. Lower levels of thyroid hormones, which control how many calories we burn at rest, can make dropping pounds harder, Tzeel says. It’s why hypothyroidism, a condition in which the thyroid gland doesn't produce enough thyroid hormone, interferes with weight loss. The same goes for other medical conditions that affect hormones involved in metabolism and appetite, like Cushing’s syndrome, polycystic ovarian syndrome, and Addison's disease.

How meal timing affects weight loss

Eating large meals late at night may potentially contributing to weight gain, plus cause heartburn, indigestion, bloating and flatulence, says Chicago, Illinois-based dietitian and advisor to Smart Healthy Living Amanda A. Kostro Miller, RD, LDN. Evolving research on time-restricted eating suggests eating earlier in the day and fasting for an extended period overnight may improve the appetite hormone ghrelin and increase fat burn, although more research is needed.

How lifestyle factors affect weight loss

Researcher have surfaced a variety of correlations between certain lifestyle factors and weight: More screen time appears to increase the odds of being overweight; Insufficient sleep is correlated with an increased risk of obesity; chronic stress or symptoms of depression and anxiety can lead to eating more, fat retention, and a lack of motivation to exercise. Lack of access to palatable foods can lead to eating more while people who live further from stores that sell healthy food are more likely to be overweight. Your social circle, family, and cultural traditions also affect your weight because they influence diet and exercise habits. Additionally, some medications (like some antidepressants, antipsychotics, and some birth control options) slow your metabolism or increase your appetite, Soloff says.

Developing and maintaining healthy eating habits

Now that you've wrapped your head around the science of weight loss, it's important to understand the pillars of healthy eating, which can help with weight control. Hint: It's not just about consuming “diet” foods—it’s about being mindful of how and what you eat, and other lifestyle factors that influence your appetite and food decisions.

To achieve healthy eating habits that set you up for optimal health, look beyond counting calories: It’s important to consume an adequate mix of vitamins and minerals, says Kostro Miller. You’ll tick that box by eating a diverse array of fruits, vegetables, lean proteins (like fish, chicken, low-fat dairy products, and soy), healthy fats (think: nuts, avocados, and olive oil), and fiber (from whole grains or from fruits and vegetables).

It’s also important to lower your intake of saturated fat, red meat, pork, processed foods, and added sugars, which can reduce your risk of adverse health outcomes (like diabetes, high blood pressure, obesity, and heart disease).

Women should aim for at least 25g of fiber, 1.5-2 cups of fruits and 2-2.5 cups of vegetables per day while men should aim for 30-38 grams of fiber, 2 cups of fruit and 2.5-3 cups of vegetables per day. The American Heart Association (AHA) advises women to cap their daily intake of added sugars at 25 grams (or 6 teaspoons) and men to cap theirs at 36 grams (or 9 teaspoons), while the USDA/DHHS is (slightly) more liberal, recommending that you cap total added sugar intake to 10% (about 200 calories of sweets on a 2,000 calorie diet). The AHA also advises limiting saturated fat intake to 5 to 6 percent of total daily calories (USDA also recommends keeping this under 10% of total calories). One gram of fat equals 9 calories; if you’re consuming a 2,000-calorie diet, that would mean about 13-22 grams max. 

Other secrets of healthy eating? “Having regular meal times so you don’t become ravenous and end up overeating,” Kostro Miller says. “And minimizing mindless snacking or eating out of boredom.” If your tummy’s rumbling after dinner, choose smaller snacks of healthy fats, lean proteins, or fiber, she advises.

The value of regular exercise 

Regular physical activity is another critical component of weight loss: While research suggests that dietary changes may be even more important than exercise in promoting measurable weight loss, in part because working out can lead to an actual increase in appetite and/or an increase in food intake to compensate for calories burned, which people tend to overestimate, evidence suggests that regular physical activity can help you keep off weight you've lost and sidestep weight loss plateaus.

The science is pretty simple: When you lose weight, your basal metabolic rate (BMR) goes down since it takes less energy to keep your body up and running. Meaning? The less you weigh, the fewer calories your body burns at rest. Because exercise builds lean muscle mass that amps up BMR, and contributes an additional caloric burn, moving even a little on most days can make all the difference in your weight loss journey.

In fact, minor movements like fidgeting, tapping your foot, or getting up from your chair to stretch multiple times throughout the day have been found to help some people burn over 100 additional calories per day.

Striving toward a healthy emotional relationship with food

Eating in response to stress or anxiety can fuel unhealthy eating behaviors that undermine your wellbeing and interfere with your weight loss efforts. Viewing food as forbidden and feeling compelled to restrain yourself from eating it can incline some people to overeat—which is particularly important to consider if you find yourself regularly restricting yourself all day, then binging or feeling too full late at night.

Instead of appraising foods as “good” or “bad,” Kostro Miller advises focusing on what they nutrients they provide: This may mean choosing fruit over a processed snack to nourish your body with nutrients and fiber. Or it may mean enjoying a reasonable portion of dessert to add variety to your eating approach. 

You can foster a more mindful relationship with eating by taking time to cook, savoring your food, and sharing meals with others. Eating with your non-dominant hand, using chopsticks, and placing your utensil down between bites also help slow you down and attend to what you're doing, Kostro Miller says.

Is the fastest way to lose weight the best way?

Highly restrictive or extreme diets may cause rapid weight loss. But that weight loss may be comprised mostly of water weight rather than fat loss, and it may not be sustainable. What’s more, it could adverse health outcomes and set you up for unhealthy eating habits. 

The nutritional imbalances wrought by some fad diets have been found to lower immunity, decrease heart health, and increase blood pressure, high cholesterol, and risk of gallbladder disease. What’s more, rapid weight loss diets often invite weight regain once dieters abandon overly restrictive eating habits, leading to a cycle of yo-yo dieting that can mess with your morale. 

On the other hand, gradual weight loss is more likely to stay off, involve fat loss, and improve physical and psychological health. 

5 weight loss tips for getting started

Losing weight doesn’t have to feel like self-punishment. Consider these research-backed techniques to lower the number on the scale while developing healthy and sustainable habits. 

1. Keep smarter snacks at the ready.

If you're craving a snack you'll likely go for what's convenient, regardless of your preference. When researchers offered undergraduates both popcorn and apples in a 2014 study, participants ate whatever was nearest them. Those closest to fruit consumed roughly 2.5 times fewer calories than those closest to popcorn. To emulate this experiment, stock your desk, office fridge, or bag with healthy snacks like fruits or veggies, and add some lean protein (like part-skim cheese) to make these nutritional powerhouses more satisfying.

2. Drink plenty of water.

Drinking water can help you eat less, especially if you empty one or more glasses before meals. A 2013 systematic review found that drinking more water helped dieters achieve their weight loss goals in part because H2O fills you up, which may reduce overall food intake. Plus, staying adequately hydrated sets you up for regular bathroom runs. Meaning? You could find yourself moving more throughout the day—a healthy practice regardless of your weight loss goal. “So often in practice I’ve see people confusing thirst with hunger—which is why I’m a big advocate for ruling out any confusion by drinking H2O before you start grazing on any nearby snack—especially if your main goal is weight-loss,” adds certified dietitian nutritionist Jackie London, head of nutrition and wellness at WW.

3. Indulge consciously. 

Living a healthy lifestyle sometimes involves compromise, but that doesn’t you can’t enjoy it. Giving yourself a choice between treats may help. Think: “Tonight, I’m choosing to have a glass of wine instead of dessert,” or vice versa. Being in the decision making seat is more empowering than feeling like you’re policing yourself.

This either/or approach also works for decisions beyond alcohol and dessert. Think: “I’m in the mood to veg out and watch TV. So I’ll either stream a show on the elliptical or I’ll take a fifteen minute walk before tuning in.” 

4. Choose “whole” foods over processed foods.

Processed foods often contain added sugars, preservatives, trans fats, and other ingredients that can contribute to weight gain by leaving you wanting to eat more. (The same goes for foods marketed as “healthy,” which may not seem as satisfying as the real deal.) Whole foods, by contrast, tend to contain less sodium and more fiber, nutrients, and satiating unsaturated fats that help promote weight loss by keeping you fuller on fewer calories and, some research suggests, independently speed up metabolism, says Nicole Avena, Ph.D., Visiting Professor of Health Psychology at Princeton University and author of Why Diets Fail. 

So what is a processed food? “Think: Roasted potatoes over potato chips; oranges over orange juice; peanut butter vs. a peanut butter-flavored protein bar; whole grains over refined grains, etc.,” London says. “The closer a food is to its natural state, the more likely it is to be better—and more satisfying!—for you.”

5. Eat plenty of fiber.

Yes, dietary fiber can aid bowel movements and alleviate constipation. But it has also been found to help regulate blood sugar, boost heart health, potentially increase longevity, and lower cancer risk. It also helps keep you fuller for longer, Avena adds, which can help moderate our caloric intake. 

Foods that are particularly rich in fiber include chia seeds, dark chocolate, almonds, popcorn, oats, raspberries, pears, artichokes, lentils, green peas, kidney beans and chickpeas, brussels sprouts, broccoli, and red cabbage, Avena says. 

5 weight loss tips to keep you on track

An irksome challenge for people trying to lose weight is the dreaded weight loss plateau—when progress grinds to a halt. “Plateaus occur when your body adapts to weight loss by slowing metabolism so you don’t burn more calories than you’re taking in,” Tzeel explains.

To overcome this hiccup in your weight loss journey, Soloff recommends working with a dietitian to increase your caloric intake for a few days, or on WW, make sure you’re eating all your daily SmartPoints® values and weeklies, too, which can kickstart your metabolism until you resume however much you were eating on the dietary plan that helped you lose weight in the first place. 

But that’s just one way to overcome a weight loss plateau. Here are five other practices to consider:

1. Engage in more exercise and physical activity.

Staying active helps burn calories, build strength, and improve heart, bone, and brain health, Tzeel says. Making time to engage in physical activity can boost self-efficacy—the belief in your ability to accomplish goals—which can improve your commitment to productive behaviors. 

The Office of Disease Prevention and Health Promotion recommends 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week, plus strength training on two days. And try not to skimp on the strength training: After all, because increasing your muscle mass delivers a mild metabolic boost, lifting weights (or your own body weight with exercises such as squats and push-ups) may help you overcome a weight loss plateau. 

Don’t have time for fitness? Multitasking can often be a game-changer: “Listening to a book, podcast, or music you love can be inspiring enough to get you to keep walking on the treadmill or take another lap around the block just to finish a chapter,” London says. “Ultimately, incorporating more movement more often into your daily routine is what will help you make healthier habits more consistently—and help you feel more confident about finding new ways to do so within your current day-to-day.”

If you really can't reach the recommended movement benchmarks, cut yourself some slack. Some exercise is better than none; a few trips up the stairs still beats being completely sedentary. 

2. Connect with others.

Fostering ties with others working towards wellness goals can help you stay motivated, inspired, and accountable. Who you know greatly influences your health behaviors, so consider including more people in your circle who encourage your efforts. Online communities and in-person workshops, exercise classes, personal coaches, and walking groups are great ways to widen your healthy social network—but feel free to get creative. Maybe an active coworker can be your new hiking partner.

3. Seek out healthy foods that fill you up.

Some foods make you feel fuller than others—typically, those rich in lean protein (like fish and poultry), fiber (vegetables, legumes, fruits, and whole grains), or water (fruits and veggies), can support weight loss goals by filling your belly without overloading you with excess calories, Avena says. They also provide more vitamins and minerals than less-filling foods, like chips, baked goods, processed meats and cheeses, or sugar-sweetened beverages. High fiber and high protein foods also move through the stomach more slowly to keep your appetite at bay.

Potatoes, oatmeal, kidney beans, Greek yogurt, eggs, soy protein (from edamame, unsweetened soy milk, and tofu) and whey protein (from unsweetened dairy products and lean protein sources), nuts, as well as most vegetables and fruits are particularly filling. A sprinkle of crushed red peppers may also help: A 2011 study suggests the seasoning can reduce hunger and enhance mindfulness as you eat, since the heat will naturally slow you down.

4. Reassess your eating habits.

It’s easy to slide into old eating habits without realizing it: After all, watching what you eat can get tiring, and stress can weaken your resolve. 

If you get off track, breaking down the events leading up to your derailment can help you recalibrate. Maybe you were too restrictive and need to include more items you enjoy in your meals. Maybe meal prepping on Sundays will help you eat healthier throughout the week. Or perhaps you just need a reminder of what you’re working towards and why: Yes, weight loss is great for self-esteem and health. But a healthy diets can improve your overall wellbeing, reduce disease risk, and boost your energy levels so you can be more present for the things and people you love, Kostro Miller says. 

5. Give yourself the credit you deserve.

Reflecting on strides you’ve already made—mastering a new healthy recipe, say, or feeling less winded when you walk uphill—is another way to keep at your goals. How about other lifestyle adjustments you’ve made—like quitting smoking, spending more time in nature, or finding ways to reduce stress? Maintaining a sense of self-efficacy and belief in your ability to make positive changes to your lifestyle can help you persevere through challenges. It also happens to come with its own health benefits.

Finding the best approach to weight loss and wellness

Wellness is a long-term life goal. But that doesn’t mean you can’t see—and feel—its results immediately. Making incremental changes can be a source of instant empowerment. Developing a better understanding of science-backed, effective wellness programs and learning how to choose these approaches over short-lived, fad diets can boost your self-efficacy, bolster your knowledge of what’s right for your body, and prevent you from being duped by untested approaches that risk impeding your wellness goals.

Eating well, engaging in more physical activity, and cultivating a more mindful relationship with food are skills you can start practicing any time—starting today. 


Katherine Schreiber, MFA, LMSW, co-author of The Truth About Exercise Addiction: Understanding the Dark Side of Thinspiration, is a social worker and freelance writer based in New York City. She specializes in working with adults with severe and persistent mental illnesses, like schizophrenia spectrum disorders. Her work has been featured by Psychology Today, Cosmopolitan, Shape, and TIME.


Reviewed by Jackie London, R.D., December 2019