If you want to lose weight, you have to be eating in a calorie deficit [1] — but cutting calories can often cause you to feel hungry and sluggish. Enter: volume eating [2], also known as volumetrics. The concept is based on The Ultimate Volumetrics Diet [3] by nutrition scientist Barbara Rolls, and it encourages people to fill up on foods that are high in volume but low in calorie density [4] — such as fruits, vegetables, soups, and whole grains [5] — while limiting portions of higher-density foods. Because these high-volume foods boast more water and fiber, they can help you feel fuller longer. It kind of sounds like a foolproof plan for weight loss, right? Ahead, experts explain how to make it work for you.

What Is Volume Eating?

"Volume eating, which was popularized by the Volumetrics franchise over 20 years ago, is a pretty simple concept," Stacie Stephenson [6], DC, a certified nutrition specialist and author of Vibrant: A Groundbreaking Program to Get Energized, Own Your Health, and Glow [7], told POPSUGAR. "Choose foods with lower energy density, and you can eat more without taking in too much energy, or too many calories."

Dr. Stephenson explained that volume eating is behind popular photos that compare 200 calories of a high-fat or high-sugar food next to another plate with 200 calories of a high-volume, low-calorie food, such as fiber-rich vegetables. "Imagine a pat of butter, or half a small cheeseburger, or just five ounces of pasta — all 200 calories — compared to 20 ounces of baby carrots, 21 ounces of broccoli, or 50 ounces of celery," Dr. Stephenson said. "What would fill you up more: two-thirds of a candy bar, or 12 ounces of black bean soup? Two-and-a-half ounces of french fries, one ounce of bacon, or one ounce of sugary cereal, or 10 ounces of grapes, 20 ounces of melon, or 50 medium-sized strawberries? How about 30 cups of spring mix?"

She added that although volume eating usually involves high-fiber vegetables, it also applies to protein. Imagine a couple ounces of ribeye compared to roughly eight or nine ounces of cod or tofu. "Fill up on vegetables, fruits, and lean protein instead of the high-fat, high-sugar foods, and you'll experience how volume eating works," Dr. Stephenson said.

It may seem counterintuitive, but Alexandra Soare [8], RDN, explained that volume eating can help you reach a calorie deficit, while adding more food to your plate. "The focus is not placed too much on 'eliminating' foods," Soare told POPSUGAR. "The idea is to create a healthy relationship with food by adding more healthy high-volume foods, usually richer in fiber and other micronutrients." This means that you can eat more food for the same number of calories, helping you to stay full throughout the day without going over your calorie limit.

Can Volume Eating Help You Lose Weight?

If followed consistently, the experts agreed that volume eating can help you lose weight. "Volume eating is a great tool that can support weight management," Kylie Ivanir, RD, a registered dietitian at Within Nutrition [9], told POPSUGAR. "One of the central tenets of weight loss is calorie balance, or taking in fewer calories than we put out. However, we do not want to feel hungry or deprived, or we will be thinking about food all day and likely end up eating beyond our needs."

With volume eating, you can feel full without overeating. Ivanir explained that this is partly because high-volume foods stretch the stomach, triggering the release of the hormone ghrelin, which signals to the body that you're full. "Volume eating therefore allows us to feel full while eating fewer calories," she said. To illustrate this point, Ivanir compared a protein bar to a salad. "A protein bar may be higher in calories, but it is dense and low in volume and will not stretch your stomach," she said. "A voluminous salad, on the other hand, that contains various high-fiber vegetables, nuts, seeds, and lean protein will cause your stomach to stretch, contributing to feelings of fullness. This will prevent overeating, thereby helping with weight management."

Trista Best [10], MPH, RD, LD, a registered dietitian at Balance One Supplements [11], has personally lost weight while volume eating. "I've been following this diet pattern for a year and have found great success in weight loss and feelings of overall improved well-being," Best told POPSUGAR. "My personal experience aside, volume eating can produce weight loss if followed appropriately. You should experience weight loss due to increased satiety from meals and lower calorie intake overall."

What Does a Typical Day of Volume Eating Look Like?

Dr. Stephenson laid out a plan for what volume eating might look like for you:

• Breakfast: A big bowl of mixed fresh berries, with or without a dollop of yogurt (she prefers plant-based types, but nonfat Greek yogurt is also fine for those who tolerate dairy).
• Lunch: A large salad filled with a variety of fresh raw veggies with some protein, such as a half cup of white beans or three ounces of shrimp.
• Dinner: Some lean protein, such as fish or air-fried tofu, with several different steamed veggies.
• Snacks: An apple, orange, or pear, or as many raw veggies as you like, with a small amount of hummus for dipping. Try making your own hummus by blending chickpeas and edamame, lemon juice, and garlic, instead of using sesame butter and added oil, for even more fiber and less fat.

"Compare this to a standard American way of eating, and you can see how this kind of regular diet will result in a normalization of body weight fairly easily, especially since you don't really have to worry about portion sizes for most plant foods," Dr. Stephenson said. "Just go easy on the higher-fat foods, including nuts and avocado, but get your protein in, and weight loss will be imminent. No need to count, tally, or fret."

She also offered one rule of thumb that will almost always maximize volume while minimizing energy density: "Stick to real whole foods without adding any oil or sugar." For example, sauté in vegetable broth and get sweetness from fruit. "Your palate will adjust quickly, and before you know it, extra sugar and oil won't be appealing," Dr. Stephenson explained.

Are There Any Side Effects to Volume Eating?

Although volume eating is generally considered healthy, there could be side effects for those who suffer from IBS. "Foods that trigger IBS are usually high volume — for example, watermelon, eggplant, broccoli, and cabbage," Soare said. "If you have undiagnosed IBS, these high-volume vegetables could set off bloating, stomach pain, constipation, and, in some cases, also diarrhea.

"As a registered dietitian, I still recommend adopting a high-volume diet," she explained. "Before starting, however, you should first find out if you suffer from IBS and adopt a specific low-FODMAP diet [12] first." Even if you don't have any digestive issues, it's always a good idea to consult your doctor before trying to lose weight.