Energy density

Energy density is also called calorie density. If you want to lose weight and maintain the loss understanding this concept is really useful. This page can be used by patients and practitioners, along with our PDF handout.

Summary, in a nutshell

Whole plant foods tend to fill you up more than other foods. This helps you lose weight. If you only want the summary picture, here it is:

Energy balance

You may have heard “Energy in vs energy out = weight loss or weight gain” and of course this is correct: If you eat more total energy (calories) than you use, you will gain weight. If you eat less energy than you use, you will lose weight.

All of your energy intake (in the left blue bar) is from your “diet”: foods and drink. Most of the energy you use daily is not from exercise. In fact, this normally is around 10% of total energy. The remaining 90% is a combination of metabolism and other.*

Small details
*Metabolism is ‘resting energy expenditure’ and is the automatic functions of life; pumping blood, growing cells, etc.
Heat from digestion is ‘thermic effect of feeding’
Non-exercise activity thermogenesis (NEAT) includes walking, fidgeting, etc.

How to change energy balance to lose weight

1. “Eat less” – Consume less food.
2. “Move more” – Expend more total energy.
3. “Diet and exercise” – Combination of the two.

Diet vs exercise

Here we see a 40% reduction in total caloric intake when switching to a whole food plant-based diet.

A whole food plant-basevd diet is roughly equivalent to 100 minutes of vigorous exercise daily.

Why are some people overweight but not others? (details)

Why are some people overweight but not others?

Just like there is a bell curve distribution for how tall people are, there are genetic differences in how people process foods (their ‘metabolism’).

When you eat foods, your body will break them down. E.g. Fat receptors will send a message back to the brain saying ‘I have eaten enough calories’. If we eat foods we didn’t evolve with, sometimes this message can be tricked.

If a lean person and an overweight person both eat the same amount of fatty food, each will process these foods differently. The lean person gets the message to stop eating at the right time, but the overweight person does not.

Surely, people just overeat?

Not so! Most people who are obese or overweight get there slowly, by having a tiny bit too much energy per day. If a person gained 8 kg between the age of 25 and 35, this would be 100 kJ of energy per day – less than 3 grams of fat!*

*People eat around 10,000 kJ a day, so 100 kJ is only 1% too much energy. If you think of someone who is maintaining their weight over a period of 10 years, just think they are regulating their energy intake to within 0.1%. Just as you don’t breathe too much or too little by accident, if you eat the right foods (whole foods with fibre in them), your body’s amazingly fine-tuned systems will measure exactly how much you have eaten and take care of the rest.

Some people have excellent receptors, and could eat a very high fat diet without gaining weight. Most people cannot. Your mechanisms to regulate how much you eat are very close but not usually perfect.

Why are plant foods so low in energy?

  • Plant foods are rich in fibre, water, and carbohydrates; this mean they are low in density.
  • Water and fibre take up a lot of space in the stomach, but only a small amount of energy is provided by fibre.
  • Carbohydrates/sugars have half the energy of fats.
  • Vegetables, e.g. broccoli or potatoes contain fibre and water which stretch out the stomach. They have protein, carbohydrates and fats in the quantities the body was designed to digest and store. In order to gain enough energy through lower density plant-based foods, we should eat a lot of starches, and this is consistent with our evolution. Potatoes are great for weight loss, however with processed oil and salt from the modern environment – deep fried potato chips from a fast food restaurant are not.


Maintenance of weight loss is hard, similar to how it takes most people multiple attempts to quit smoking. Lifestyle changes are hard, so don’t be disappointed by inevitable set backs. Creating unrealistic expectations for yourself by making yourself change when you are not ready won’t help. Give it your best effort.

  1. Start with making simple changes first, like cutting added fats from cooking, or removing dairy products.
  2. It’s important to monitor progress, and work out solutions to problems as they arise. GP consults are perfect for this; start by getting cholesterol, HbA1c, blood pressure, weight and waist circumference measured.
  3. Don’t pressure others to change – they’ll ask if interested.

So, that’s energy density, one of the principles that is important for losing and maintaining weight loss.

  • If you would like some more information, we explain this and more in our video series. Try the first week of the video programme here for without making an account (like on facebook) or choose a free video programme here
  • Click here to see our traffic light system.
  • If you want to see the full page graph of lots of different foods and their energy density, click here (opens in new page).

Download a handout with the above information on energy density (PDF)

Download a graph of lots of different food items(PDF)

Dr Nicholas Wright