What Is the Volumetrics Diet and Should You Try It? Here's What a Dietitian Has to Say

There are so many different fad diets that it can be hard to keep track. While they can vary in their recommendations, weight-loss claims are common. But certain plans can be easier to sustain than others. Most diets focus on restriction, which can lead to hunger and overeating, and might make it difficult to sustain the diet and any associated weight loss over time. In contrast, the volumetrics diet aims to reduce hunger by focusing on nutrient-dense foods that fill you up without a lot of calories. Here we dive into what the volumetrics diet is, the pros and cons of the diet and a sample volumetrics diet meal plan.

What Is the Volumetrics Diet?

The volumetrics diet was created by Barbara Rolls, Ph.D., a professor, researcher and director of the Laboratory for the Study of Human Ingestive Behavior at Penn State University. The principles are outlined in her book, The Ultimate Volumetrics Diet: Smart, Simple, Science-Based Strategies for Losing Weight and Keeping It Off. The goal is to feel full on fewer calories by filling most of your plate with nutrient-rich, low-calorie foods. Think: fruits, vegetables, soup and salad. The volumetrics diet plan puts the focus on what you can eat instead of what you can't eat and doesn't require counting calories or grams of macronutrients (like fat, carbs or protein).

Foods are categorized by energy density (also called calorie density). High-energy-density foods are foods that have more calories and fewer nutrients per calorie. Low-energy-density foods are full of nutrients and have a lot of nutrients per calorie, but don't have many calories. Low-energy-density foods, like fruits and vegetables, also tend to have a higher water content. When you eat mostly low-energy-density foods, you can eat a higher volume of food while consuming fewer calories, since these foods tend to be high in fiber and water but low in total calories.

For example, 5 cups of popcorn and 15 potato chips both have about 160 calories. You can have a lot more popcorn than chips for the same number of calories because popcorn has a lower energy density. You get more volume, hence the name volumetrics diet.

What Can You Eat on the Volumetrics Diet?

No foods are off-limits on the volumetrics diet, regardless of their caloric density. Instead, the focus is on eating more low-energy-density foods like fruits, vegetables, soup and salad and fewer high-energy-density foods like fried foods, cheese and desserts.

The volumetrics diet categories foods into four categories based on energy density.

Category 1: Very-Low-Energy-Density Foods (less than 0.6 calories per gram)

Examples of very-low-energy-density foods include chicken noodle soup, lentil soup, most fruits, nonfat yogurt, and nonstarchy vegetables like tomatoes, peppers, mushrooms, broccoli, asparagus.

Category 2: Low-Energy-Density Foods (0.6-1.5 calories per gram)

Examples of low-energy-density foods include split pea soup, clam chowder, tofu, potatoes, beans, grapes, bananas, low-fat yogurt, bran cereal, whole-wheat pasta, light tuna, turkey breast, tomato pasta sauce.

Category 3: Medium-Energy-Density Foods (1.6-3.9 calories per gram)

Examples of medium-energy-density foods include hummus, avocados, feta, part-skim mozzarella, tortilla, pita, bread, chicken breast, egg, salmon, lean ground beef, ice cream, pretzels, light mayonnaise.

Category 4: High-Energy-Density Foods (4-9 calories per gram)

Examples of high-energy-density foods include butter, wheat crackers, bacon, desserts, chips, chocolate, peanut butter, nuts, jelly, full-fat sauces like ranch and mayonnaise and olive oil.

There's no specific formula, guideline or amount of food from each category you have to follow. Rather, the idea is to track a few days of what you currently eat and then look for places in your diet where you can swap high-energy-density foods with lower-energy-density foods. Small swaps over time can create a calorie deficit that can help lead to weight loss while keeping you feeling full and satisfied.

Making half your plate fruits and vegetables is a simple way to create a meal of very-low-energy-density foods. Lean protein, low-fat foods and fiber- and water-rich foods are also emphasized. In her book, Rolls recommends starting meals with a veggie-packed dish like a soup or salad to help you fill up on fiber and water before consuming the rest of the meal.

In addition to dietary swaps, the volumetrics diet plan encourages physical activity, specifically working up to 10,000 steps per day, as well as tracking food and weight. Mindset and habit hacks are also included, like treating yourself with nonfood rewards.

Volumetrics Diet Pros and Cons

As with any weight-loss diet, there are both positive and negative things to consider if you are interested in the volumetrics diet. Here are some of the pros and cons of following the diet.

Pros

• Don't have to count calories or macros
• No foods or drinks are off-limits
• Puts focus on eating more, rather than eating less
• Might be a more flexible, sustainable plan
• May improve gut health by increasing variety of nutrient-rich fruits and vegetables

Another positive thing about the volumetrics diet is that there are some scientific studies about its efficacy. Older research found that reducing high-energy food intake (like fats), while simultaneously adding low-energy-density foods like fruits and vegetables, led to weight loss and increased satiety. However, more recent research is challenging these findings. Some studies suggest that other factors like the gut microbiome and genetics might influence weight-loss results when following the volumetrics diet. More research is needed to clarify the efficacy of the volumetric diet for weight loss.

Cons

• Requires cooking most meals at home
• Limits fats, even nutrient-rich fats like nuts, olive oil and avocados
• Calculating energy density of foods is time-intensive
• May not be structured enough for some people

While there are some pros to the volumetrics diet, there are also several cons. Classifying foods into categories based on energy density can be challenging and time-consuming. Incorrectly calculating a food might lead to inaccurately following the diet. Also, being required to cook most meals at home might be time-consuming, expensive and not realistic for some people.

Sample Volumetrics Diet Meal Plan

The volumetrics diet plan allows for breakfast, lunch, dinner and two to three snacks. Dessert can also fit into this meal plan. Rolls' book includes four weeks of sample meals and menus that can be mixed and matched, as well as over 100 recipes that incorporate low-energy-density foods.

Here's an example of a day of eating on the volumetrics diet plan.

Breakfast

• Oatmeal made with skim milk, ¼ cup blueberries, 2 Tbsp. raisins, 1 Tbsp. sliced almonds

Snack

• Low-fat Greek yogurt with berries

Lunch

• Starter salad with mixed greens, cucumbers, tomatoes, carrots and 2 Tbsp. light Italian dressing
• Turkey sandwich on whole-wheat bread with 3 oz. turkey, 1 slice of cheese, light mayo, mustard and vegetables of choice
• 1 apple

Snack

• Bell peppers and hummus

Dinner

• Vegetarian Chili
• 1 square dark chocolate

So, Should You Try the Volumetrics Diet?

If you are looking to lose weight, the volumetrics diet is one option for a plan that might help you achieve your goals. With a focus on adding nutritious foods and feeling full, this diet might be more sustainable long-term that other more restrictive diets. There's no calorie counting and all foods can fit with some planning, which might make the plan feel more flexible. That said, the diet can be time-consuming and require more cooking at home. It also has less structure than some other eating patterns. Aside from weight loss, adding more fiber-filled, water-rich fruits and vegetables to your diet can offer a slew of other health benefits, including supporting a healthy gut and decreasing risk of heart disease, diabetes and cancer.