What is the volumetrics diet?

How does the volumetrics diet work?

The volumetrics diet separates foods into four main categories, based on their calorie density. Foods that are high in water and low in calories, such as carrots, are a very low calorie density food, compared to something like chips, which is high calorie density.

The volumetrics diet suggests eating 1,400 calories a day, and it also recommends 30-60 minutes of exercise a day.

How does the volumetrics diet work?

The four main categories of food, based on their calorie density, are:

• Category 1 – very low calorie density (calorie density of less than 0.6)
• Category 2 – low calorie density (calorie density of 0.6–1.5)
• Category 3 – medium calorie density (calorie density of 1.6–3.9)
• Category 4 – high calorie density (calorie density of 4.0–9.0)

Dr Rolls’s book provides full information on how to calculate the calorie density of different foods, as well as recipes, but a general rule is that you divide the number of calories in a particular serving size by its weight in grams, and you will end up with a figure between zero and nine.

For example:

• One portion of your five-a-day is 80g carrots, which is 35 calories
• 35 (calories) divided by 80 (grams) = 0.43
• Carrots are therefore a category 1 food

What does high volume, low calorie mean?

All foods have an energy density based on their calorie content. 'High volume' refers to foods that contain a lot of water or fibre, but little to no calories. These foods can then be consumed with less attention to portion sizes or number of calories, but they will be more filling because of the volume they add.

Examples of high-volume, low-calorie foods include lettuce, celery, broccoli, berries and cucumbers.

What can I eat on the volumetrics diet?

No food is off limits, but if you consume foods that are in category 3 or 4, you need to adjust your portion sizes and other meals to accommodate for any high calorie density foods that you may have.

• Category 1 forms the foundation of the diet, as the foods in this category are high in water and fibre, and should make you feel fuller. This includes foods such as bananas, apples, carrots and soups.
• Category 2 foods are healthy, but to be eaten in moderation, such as skinless chicken, lentils, potatoes and brown rice.
• Category 3 foods are classed as being healthy, but should only be eaten in small quantities, for example, salmon, cheese and refined carbohydrates such as pasta and white bread.
• Category 4 foods are processed, high-sugar, high-fat foods, which should be consumed sparingly, including nuts and seeds, butter and processed foods such as chips.

What foods should I avoid?

Rather than avoiding foods, the volumetrics diet is about limiting certain categories of food, especially those that fall into category 4, such as processed foods like chips and pizza, and high-fat meats such as bacon and poultry with skin on. The volumetrics diet also recommends limiting some of the healthy high-fat foods like nuts and olive oil, because of their high calorie content. The key is also to stay within the recommended 1,400 calories a day.

Is the volumetrics diet healthy?

There is limited evidence for the volumetrics diet and any studies that have been conducted do focus on the weight loss aspect of the diet. Benefits include:

Promotes weight loss

A small 2014 study found that an energy density diet based on the volumetrics diet had better weight loss outcomes compared to those following a meal replacement plan. However, obesity is often complex, and this study had no positive effect on those who may struggle with comfort eating. Also, physical exercise decreased as more time went on.

Helps reduce BMI (Body Mass Index)

A larger study by Dr Rolls et al found that those who follow a diet in very low or low energy density foods, as seen in the volumetrics diet, have a lower BMI and waist circumference.

May help reduce the risk of diabetes

Research indicates that low energy density diets may help improve fasting blood sugar levels, as well as weight loss, thereby reducing the risk of type-2 diabetes. Reducing ultra-processed foods, or category 4 foods, also reduces the risk of developing type-2 diabetes.

May improve diet quality

The foods found in categories 1 and 2 are essentially low-calorie whole foods, such as fruit, vegetables and lean proteins. These naturally contain more micronutrients, such as vitamins and minerals, as well as fibre – this would improve diet quality compared to a diet that is high in category 4 foods, which are low in micronutrients but high in sugar.

Research also indicates that diets low in ultra-processed foods also have a lower risk of conditions such as heart disease, cancer and premature death.

Tips for volume eating

• Add fruit or vegetables to every meal: grating an apple into your morning porridge, adding mushrooms to your mince or having a salad with your evening meal is an easy way to start adding low calorie density foods to your diet
• Swap dried fruit for fresh fruit: fresh fruit naturally has a higher water content than fruit that has been dried
• Eat more raw vegetables: cooking vegetables reduces both bulk (as most vegetables tend to reduce in size when cooked) and water content, so raw vegetables will promote a slightly greater satiety
• Add extra egg whites to your eggs: if you are making scrambled eggs or an omelette, increase the number of egg whites that you use. Egg whites are included as a category 1 food as they are low calorie density
• Have soup: vegetable and broth-based soups, such as chicken broth, can be consumed freely on the volumetrics diet
• Swap crisps for popcorn: popcorn has higher volume because of the added ‘air’ and is a better snack option on the volumetrics diet

A nutritionist’s view

Overall, the volumetrics diet has some good principles, in that it focuses on consuming more whole foods that are high in fibre and nutrients, such as fruit and vegetables, and less high calorie density foods, such as processed and ultra-processed foods. We know that diets high in processed and ultra-processed foods contribute to obesity but also increase the risk of type-2 diabetes and heart disease.

Satiety is often a challenge in those looking to lose weight, and compared to low-calorie diets that focus purely on calorie counting and don’t consider the nutrient status of the food being consumed, the volumetrics diet does appear to offer potential benefits. However, it is a time-consuming diet in that it requires time to find recipes, plan meals and calculate the calorie density of each food or meal. If you are someone who has a busy lifestyle or doesn’t enjoy preparing their own food, then this may not be suitable for you.

The volumetrics diet is one that's high in fruit and vegetables, which also means it is high in fibre. Fibre is essential for a healthy digestive system and gut microbiome, but if you struggle with digestive issues such as IBS (Irritable Bowel Syndrome), then the increased fibre in this diet may aggravate your symptoms.

There are some downsides to this diet though. Foods such as nuts, seeds and olive oil appear in the high calorie density group (category 4 foods), which means they are supposed to be consumed sparingly; but, research has long indicated that these foods do have many health benefits, as well as forming a key part of the Mediterranean Diet which is known for increasing lifespan and healthy aging.

Any diet that is ultimately based on calorie counting, even if the density of foods is better, doesn’t always address eating behaviours or challenges, so while the volumetrics diet does appear to be a healthier weight loss approach, this also needs to be considered. And, as with any diet that requires any form of reduced calorie or restricted, it is recommended that you seek medical advice, especially if you are pregnant, breastfeeding or on any medication.

Does the volumetrics diet work?

For some, the volumetrics diet can offer weight-loss benefits if you have the time to plan and track the calorie density of the food you are consuming, but are also looking for longer-term healthy eating rather than a quick fix to drop a few pounds. It isn’t for everyone though, and it is still a calorie-counting diet, which may lead to unhealthy eating behaviours and feel restrictive for someone who is very busy or doesn’t have time to prepare their own food.

Want more like this?

10 weight-loss myths busted
How to lose excess weight: Healthy Diet Plan
How much fibre should I eat every day?
What is diabetes?
How to eat to manage diabetes – top 10 tips
Health benefits of magnesium

Nicola Shubrook is a qualified nutritionist registered with the British Association for Nutrition and Lifestyle Medicine (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at urbanwellness.co.uk.

All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.