When you’re dieting, it seems you’re always counting: calories, carbs, pounds, or ounces. You’re either measuring what you’re eating, weighing to see what you’ve lost, or crunching numbers on meals and snacks. Dieting is a numbers game, but which numbers are most important to track?
Dietitians and doctors are divided over the benefits of low-calorie and low-carb diet. Numerous studies and meta-analyses have examined the benefits of each when it comes to shedding pounds. Even more studies have examined other healthfulness aspects of both weight-loss programs, including changes to cholesterol, blood sugar, body composition, blood pressure, and more.
But when it comes to the nuts and bolts of shrinking your waist, which diet does science say is more likely to be a success? The truth is both. One diet may work well for some people, but perhaps not for others. That’s why understanding each diet style is important before you take the leap into losing weight with a restrictive plan.
Read on to find which diet’s pros and cons fit your lifestyle better and which might help you be successful.
Why a low-calorie diet is successful
It’s easy to follow. The average low-calorie diet is based on a 1200- to 1500-calorie-per-day goal. (Your precise goal depends on your weight, your activity level, your gender, and your age.) Beyond that number, you’re able to eat almost anything you’d like, which provides for greater flexibility and customization. Many packaged foods list calories and nutrients per serving, so you can subtract each meal or snack from your total. If you’re cooking or eating something that doesn’t come with a nutrition label (a banana, for example), many web sites and smartphone apps can be a valuable resource for getting accurate information.
It’s supported by research. For decades, studies have supported the calories-in-calories-out strategy of weight loss. A calorie deficit (eating fewer calories in a day than your body requires to perform daily tasks) helps your body turn to burning fat stores for energy, which means you’ll begin shedding pounds you’ve been carrying around. Short yourself 500 to 1000 calories every day, and you can (at least according to the math) drop one to two pounds per week.
You can eat a variety of foods. Many extreme diets require you to eliminate or at least severely restrict specific foods, or entire food groups altogether. With a low-calorie diet, you don’t have to restrict foods groups—nothing is “off limits,” per se—but you might have to restrict your portion size. So can you eat chocolate? Sure. You can have a square or two, not the whole bar.
Why a low-calorie diet isn’t successful
The diet can lead to hunger and low energy. You’re eating less now than you did before, and your body will need time to acclimate to your reduced food intake. That may make your tummy rumble more frequently. It may also lead to sagging energy levels. Food provides fuel, and when you cut your intake, your body has to look elsewhere for natural energy.
You have to follow the diet for life. This may not be welcome news if you want to lose weight and keep it off for the rest of your life, but here’s the truth: You likely will need to follow some version of a low-calorie diet for the rest of your life to sustain your success. There will never be a return to “typical” eating. Instead, this lower-calorie philosophy needs to become your lifestyle, not the exception to the rule.
The food isn’t always healthful. If you’re aiming to eat 1,200 calories each day, you can get those 1,200 calories from virtually anything—fruits and vegetables or chocolate cake and ice cream. Reducing your calorie goal won’t necessarily boost your intake of nutrient-rich food. You have to make eating more whole foods a priority of this strategy.
Why a low-carb diet is successful
It’s very satiating. Fat and protein are filling, and a low-carb diet often makes up for lost carbs with those two macronutrients. When eating a low-carb diet, you may feel fuller longer after each meal, which reduces your cravings for snacks and in-between bites.
You may see results more quickly. Excess carbohydrates are stored in your muscles and liver as glycogen, your body’s favorite immediate energy source. Those glycogen stores hold water, so when you cut carbs, your body begins using the glycogen for energy until it’s all gone. As the glycogen levels shrink, so does the water they’re holding, so you may see the results of lost “water weight” within the first few days of a low-carb diet. Additionally, cutting carbs lowers the level of insulin, a hormone that signals your body to store fat.
Many low-carb plans let you eat foods you can’t eat on other diets. High-carb foods, like fruits, some vegetables, and sweet treats, are off limits with low-carb diets, but foods many other diets eliminate are here. Bacon, butter, cheese, and red meat, which are often the first on the chopping block with other diets, are allowed in a low-carb diet.
It eliminates a lot of high-carb, low-nutrition foods. A low-carb diet restricts what carbs you can eat, and this diet could help you eliminate foods that are nutritionally void, such as high-sugar foods, drinks, desserts, and snacks. Processed, high-carb foods also pack a lot of calories, so eliminating those can reduce your daily calorie intake, too.
A low-carb diet may reduce your risk of diseases, including type 2 diabetes. By decreasing carbs, you can naturally lower your insulin levels, which causes the body to burn more stored fat for energy. One study suggests people who are overweight and have either a risk for diabetes or existing metabolic syndrome saw greater weight loss and more successful changes in health markers, like insulin sensitivity, after following a low-carb diet for six months than people who followed a traditional low-fat diet.
Why a low-carb diet isn’t successful
You have to eliminate many healthful foods, like fruits and vegetables. The list of foods you can eat on a low-carb diet is short. Healthy carbs, such as whole grains, fruits, starchy vegetables, and legumes, are on that list. These foods are rich in carbs, yes, but they also have vitamins and minerals that are important to maintain good health and prevent nutrition deficiencies.
You may gain weight back quickly when you return to “normal” eating. When you reintroduce carbs, your glycogen stores will return, and with them comes them “water weight.” That means you may see a rapid increase on the scale once you stop restricting carbs.
Side effects include constipation, diarrhea, fatigue, and more. Without fiber, your bowel movements may become abnormal, if not almost absent altogether. Fiber, which is present in a lot of high-carb foods like fruit and vegetables, is vital to stool formation. Without it, you may find that you need fewer bathroom breaks, but you may also experiencing stomach cramps and bloating.
You have to closely track your carb intake each day. Keeping a count on how many carbs you’re eating can be time consuming, but if you’re trying to stay under a certain number (especially a really low-carb plan like Keto), you have to track. Packaged foods have the nutrition info on the label, but you’ll need to seek out reliable sources for nutrition information on foods you eat that don’t come in a package.
It may put a damper on your social life. Not all menus are low-carb friendly, so this diet could limit your choices in restaurants or reduce your desire to go out for happy hour. With low-calorie diets, you can often restrict your portion sizes and still maintain your busy social calendar.
Which is better: A low-calorie diet or a low-carb diet?
A 2010 study found that differences in weight loss and improvements in health markers were not significantly different between low-carb and low-calorie dieters. Most research suggests that over time, people using both diets ultimately reach the same weight-loss results.
Finally, a study of 46 overweight men found that low-carb diets and low-calorie diets were both successful at reducing waist size, fat mass, and total body weight. However, both groups of men were told to eliminate added sugar, refined carbs, and processed foods as part of their weight-loss experiment. This study suggests the quality of the food you eat may be a vitally important part of the weight-loss strategy you select.
Bottom line: Studies support both diet styles for weight loss. Therefore, what’s most important is finding an eating style that you can stick with—and enjoy—over time.
Find a plan that’s right for you
Our Low-Calorie Meal Plan can help you keep calories in check and watch your waistline. Each week, we deliver seven delicious dinners, each clocking in under 500 calories. If you need a whole-day strategy, we also offer low-calorie breakfast and lunch plans.
Andrea Kirkland, MS, RD and Mary Creel, MS, RD contributed to this story.