The Volumetrics diet was developed by Dr. Barbara Rolls, a nutrition professor at Penn State University, with the intention of creating a dietary approach that emphasizes healthy eating patterns rather than a structured, restrictive diet.
The Volumetrics series of books is centered around dietary “energy density” and “nutrient density.” Foods with high energy density have a higher calorie content in a given portion, while those with low energy density have fewer calories per portion. Similarly, foods that are nutrient-dense provide high levels of nutrients relative to the calories they contain, often having little or no saturated fat, sodium or added sugars.
The Volumetrics diet emphasizes eating low-energy-dense, high-nutrient-dense foods like fruits, vegetables, whole grains and low-fat dairy. Conversely, high-energy-dense foods, such as those with a high proportion of unhealthy fats or sugar and little moisture, are recommended to be limited. The idea is that by focusing on eating foods that are lower in calories and higher in water and important nutrients like fiber, the body will feel satisfied while still losing weight.
Guidelines for the Volumetrics diet
Instead of singling out specific foods or food groups to avoid, the Volumetrics philosophy is more about what to eat. Foods are divided into four groups based on their energy density that help with meal planning and portion control.
Group 1: Foods including non-starchy fruits and vegetables, nonfat milk and broth-based soups
Group 2: Foods including starchy fruits and vegetables, grains, breakfast cereal, low-fat meat, legumes and low-fat mixed dishes
Group 3: Foods including meat, cheese, pizza, French fries, salad dressing, bread, pretzels, ice cream and cake
Group 4: Foods including crackers, chips, chocolate candies, cookies, nuts, butter and oil
Foods contained within Group 1 are very low in energy density and are considered “free” foods to eat any time. The energy density increases from Groups 2 to 4, so more attention to portion control is needed with foods in these groups to avoid excess energy intake. Portion sizes and specific inclusion of groups will vary from person to person, but most will fall into a similar pattern of three meals and two to three snacks each day. Followers of the Volumetrics diet can keep track of what they eat and drink in a food record to monitor progress and identify common patterns, but exact measurements aren’t required. In addition to the food component, the Volumetrics diet provides specific plans for increasing exercise to at least 30 minutes per day most days of the week, an amount supported by the 2018 Physical Activity Guidelines for Americans.
One of the benefits of the Volumetrics diet is that it doesn’t put any foods on a “do not eat” list, which gives people the freedom to choose where high-nutrient-dense foods and drinks fit within their overall eating pattern.
Some research suggests that the more we restrict a particular food or food group, the more we want it, so building in “room” for certain favorites offers a healthier way of framing caloric splurges. Specifically, small portions of foods considered to be healthy and energy-dense, like common cooking oils (e.g., olive and canola oils) and nuts (e.g., almonds and walnuts), are recommended. These foods provide essential fatty acids that our bodies use for vitamin and mineral absorption, energy production and maintaining cell health; and this diet acknowledges that they are important to include rather than skip altogether.
The Volumetrics diet and health
While more analysis is needed on the role of energy density in weight management and the prevention of overweight and obesity, there is research supporting the use of a low-energy-dense diet to improve appetite control and help achieve weight-loss goals. By emphasizing whole foods and personalization of the diet rather than cutting out entire food groups or placing strict rules on food consumption, the Volumetrics diet is likely to be a more sustainable eating pattern than popular, quick-fix fad diets.
Some research has also been done on the connection between energy density and specific health outcomes:
- Cardiovascular disease: Some research suggeststhe potential for a low-energy-dense diet to benefit factors affecting cardiovascular disease, but sufficient evidence is lacking to fully support this.
- Type 2 diabetes: In a large observational study, women who ate diets higher in energy density had a higher risk of developing type 2 diabetes as compared with women who followed a lower-energy-dense diet.
- Breast cancer: One large observational study determined that women who had the highest-energy-dense diet had a higher risk for postmenopausal breast cancer compared with women who followed the lowest energy-dense diet.
- Weight loss: Several systematic reviews and meta-analyses of observational studies have found lower-energy-dense diets to be associated with lower body weights. Evidence from randomized controlled trials have also shown lower-energy-dense diets to be helpful for weight management and weight loss maintenance.
Most of these condition-specific studies have been observational in design, meaning that they can’t prove cause and effect like randomized controlled trials (RCTs) can (that is, that a lower-energy-dense diet caused a lower risk for disease development). Studies on the impact of energy density on body weight have been tested in RCTs with positive results. That said, larger and longer-term RCTs are needed to fully understand the effects of energy density on specific health conditions and in different populations.