Most diets ask you to eat less. The Volumetrics diet asks you to eat smarter, specifically by choosing foods that deliver more volume, more water, and more fiber per calorie, so your stomach signals fullness before you have overshot your calorie target for the day. Created by Dr. Barbara Rolls, a nutrition scientist at Penn State University, the approach is built on the well-established principle that people tend to eat a consistent weight of food each day regardless of its calorie content, and that loading your plate with low-energy-density foods exploits that tendency in your favor.
A meta-analysis of 13 randomized studies confirmed that the total amount of food eaten is the main determinant of satiety, and that a diet based on low-calorie-density foods leads to reduced energy intake and subsequent weight loss. An additional study found that people who reduced fat intake while increasing water-rich foods like fruits and vegetables lost significantly more weight than those who only reduced fat, despite eating a greater volume of food. For a full explanation of how the diet works, the science behind energy density, and a meal plan framework, see our companion article The Volumetrics Diet Plan for Weight Loss: Eat More, Weigh Less.
How the Volumetrics Four-Category System Works
The Volumetrics diet organizes every food into one of four categories based on its energy density, calculated by dividing calories per serving by the weight in grams.
Category 1 (energy density under 0.6): Eat freely. These are the foundation foods. Most non-starchy fruits and vegetables, broth-based soups, and nonfat dairy fall here.
Category 2 (energy density 0.6 to 1.5): Eat as the bulk of every meal. Whole grains, lean proteins, legumes, and low-fat dairy fill this category. These form the structural center of each meal.
Category 3 (energy density 1.6 to 3.9): Eat in smaller portions. Denser breads, full-fat cheese, higher-fat meats, and some packaged foods. These are not off-limits, just portion-managed.
Category 4 (energy density 4.0 to 9.0): Eat rarely and in small amounts. Oils, butter, nuts, seeds, processed snack foods, candy, fast food. High in calories per gram, low in the water and fiber that create satiety.
Volumetrics Diet Foods List: What to Buy
Category 1: Fill Your Plate Freely
Water-rich non-starchy vegetables:
- Cucumber and zucchini
- Celery and lettuce
- Tomatoes and bell peppers
- Broccoli and cauliflower
- Spinach, kale, and other leafy greens
- Asparagus and green beans
- Mushrooms
- Carrots and beets
Water-rich fruits:
- Watermelon, cantaloupe, and other melons
- Strawberries and other berries
- Oranges and grapefruit
- Apples and pears
- Peaches and plums
Broth-based soups and broths:
- Low-sodium vegetable or chicken broth
- Broth-based soups with vegetables
Nonfat dairy:
- Skim milk
- Nonfat plain yogurt
Category 2: Build Every Meal Around These
Whole grains:
- Oats and oat bran
- Brown rice and quinoa
- Whole wheat bread and pasta
- Barley
Lean proteins:
- Skinless chicken breast and turkey
- White fish such as cod, tilapia, and halibut
- Salmon and other fatty fish, in regular portions
- Eggs and egg whites
- Low-fat cottage cheese and Greek yogurt
Legumes:
- Lentils, chickpeas, and black beans
- Edamame
- Split peas
Low-fat dairy:
- Low-fat milk
- Low-fat plain yogurt
Category 3: Manage Portions Carefully
Higher-fat proteins:
- Salmon and fatty fish, counted in normal portions
- Lean red meat such as sirloin or tenderloin, in moderate portions
- Full-fat cheese, in small amounts
- Whole eggs, as opposed to whites only
Denser starches and breads:
- White bread and refined pasta, in smaller servings
- Dried fruit, in small portions
Category 4: Eat Very Sparingly
Limit significantly:
- Oils and butter, including olive oil in large amounts
- Nuts and seeds, which are nutritious but very energy-dense
- Packaged snack foods and chips
- Candy, pastries, and baked goods
- Fast food
- Full-fat cream and cream-based products
Practical Volume-Boosting Strategies
Start every meal with a broth-based soup or large salad. Cleveland Clinic’s dietitian review of Volumetrics notes that starting a meal with low-density foods like soup or salad is one of the most consistently effective strategies for reducing total calorie intake at that meal.
Add water-rich vegetables to everything. Stirring diced zucchini into pasta sauce, adding mushrooms and spinach to scrambled eggs, or folding grated carrot into ground turkey all increase volume and fiber without meaningfully increasing calories.
Swap cooking methods that concentrate calories for those that add water. Steaming, poaching, and boiling add moisture to foods while grilling, roasting, and frying reduce their water content and raise energy density.
Volumetrics Diet Grocery List by Store Section
This list covers one week for one adult following the Volumetrics approach, organized with Category 1 and 2 foods making up the bulk of purchases.
Produce (Category 1 Priority)
- Cucumber, zucchini, and celery (2 each)
- Tomatoes and bell peppers (4 each)
- Broccoli and cauliflower (1 head each)
- Spinach and leafy greens (1 large bag)
- Mushrooms (300g)
- Carrots (500g)
- Asparagus and green beans (1 bunch and 1 bag)
- Watermelon or cantaloupe (1 small)
- Strawberries and mixed berries (1 to 2 punnets)
- Oranges and grapefruit (4 and 2)
- Apples and pears (4 each)
Meat, Seafood, and Eggs (Category 2)
- Skinless chicken breast and turkey (600g combined)
- White fish such as cod or tilapia (2 to 3 portions)
- Salmon (2 portions)
- Eggs (1 dozen)
Dairy (Category 1 and 2)
- Skim or low-fat milk (1 carton)
- Nonfat or low-fat plain yogurt (1 large tub)
- Low-fat cottage cheese (1 tub)
Grains and Legumes (Category 2)
- Oats (1 container)
- Brown rice and quinoa (500g each)
- Whole wheat bread and pasta (1 loaf and 1 box)
- Lentils and black beans (2 to 3 cans)
- Edamame (1 bag)
- Low-sodium vegetable or chicken broth (2 to 3 cartons)
Pantry (Category 3 to 4, Used Sparingly)
- Olive oil, used in small amounts (1 bottle)
- A small portion of nuts or seeds for occasional use (100g)
Frozen
- Frozen mixed vegetables, no sauce or added fat (1 to 2 bags)
- Frozen berries (1 bag)
- Frozen fish fillets (1 bag)
Beverages
- Water, the most volumetrics-aligned beverage
- Herbal and green tea without added sugar
- Broth for drinking warm between meals
Practical Tips for the Volumetrics Diet
Think in terms of water and fiber, not just calories. The fastest shortcut to eating volumetrically is asking “how much water and fiber does this have?” rather than only checking the calorie count, since water and fiber are what physically fill your stomach.
Batch cook broth-based soups at the start of each week. A large pot of vegetable or chicken soup gives you a ready-made Category 1 meal starter for every lunch and dinner, making the strategy practical on busy days.
Use the swap principle rather than strict restriction. Volumetrics works well when you swap rather than eliminate: replace half your pasta with zucchini noodles, stretch ground meat with lentils, or add an extra cup of chopped vegetables to any dish.
Limit nuts and olive oil even though they are nutritionally healthy. This is the most counterintuitive element of Volumetrics for people familiar with Mediterranean-style eating. Nuts, seeds, and oils are genuinely nutritious but have energy densities in the Category 4 range, which means large portions undercut the volume-per-calorie principle even when the fat quality is excellent.
Drink water before and during meals. Water has zero energy density and contributes to the sense of stomach fullness that the entire diet is built around.
Do not use Volumetrics as a reason to avoid all fat. The goal is managing energy density, not eliminating dietary fat. Small portions of higher-density foods are built into Category 3 and can be incorporated at any meal without derailing the approach.
Track your meals for the first one to two weeks. WebMD’s Volumetrics review notes that calorie awareness is a meaningful component of the plan, particularly in the early weeks, since the energy density system only works as intended when you understand roughly how many calories you are taking in alongside volume.
The Bottom Line
The Volumetrics diet is built on one of the most robustly supported ideas in nutrition science: that people eat a consistent weight of food each day regardless of its calorie content, and that choosing foods with more water and fiber per calorie lets you eat the same physical volume for fewer calories. Fill your grocery cart primarily with Category 1 non-starchy vegetables and water-rich fruits, build meals around Category 2 whole grains, lean proteins, and legumes, start each meal with broth-based soup or a large salad, and treat Category 4 oils, nuts, and processed snacks as genuine rarities rather than daily staples. No food group is forbidden, nothing requires counting beyond an awareness of energy density categories, and the diet is flexible enough to accommodate most dietary needs and preferences.
Disclaimer: Nutritional data referenced in this article is sourced from USDA FoodData Central. This article is for informational purposes only and does not constitute medical or dietary advice. People with conditions that affect appropriate food volume, including gastroparesis, IBD, or IBS, should consult their doctor before adopting a high-volume, high-fiber dietary approach.
