Whenever you hear a conversation around calories and weight loss, the saying “negative calorie” will invariably come up. Typing it into Google will give you over 6 million results (it also says that a negative calorie is -4.14 kJ but that’s another story). There is a large amount of information out there, but no scientific studies that have proved the theory of negative calories.
What is a “negative calorie?”
The saying negative calorie is used to describe a process whereby it is claimed that, when you eat and digest a food, your body uses more calories to digest that food than the actual calories contained in it. The most popular example you may have heard of is celery.
To fully understand this issue it is important to look at metabolic energy expenditure in humans.
Metabolic Energy Expenditure?
Metabolic energy expenditure describes how your body uses energy. It can be broken down into 3 processes:
- Basal metabolic rate (BMR) – this is the energy cost associated with keeping the body functioning at rest
- Diet-induced thermogenesis (DIT) – this is also referred to as the thermic effect of foods. It is the body’s increase in metabolism following the ingestion of food. It accounts for the energetic costs of postprandial processes such as food breakdown, enzyme synthesis, peristalsis and nutrient uptake/assimilation. It is typically responsible for about 10% of daily energy expenditure in humans (1)
- Active metabolic rate (AMR) – the energy expenditure resulting from daily physical activities.
Diet Induced Thermogenesis (DIT)
DIT is the important factor to consider when looking at negative calories. Macronutrient composition (energy, protein and fat) play a large role in DIT and all raise energy expenditure differently. For example protein requires the greatest energy expenditure in DIT (20-30%) followed by carbohydrates (5-10%) and fats (0-3%). So this means that if you were to eat 100g of protein your body would use 20-30 calories to break down and digest the protein (1).
What Does This Mean?
Negative calories are a myth. The most important thing to remember is that all foods contain calories – yes even celery. The foods that are touted as having negative calories are things like fruits and vegetables, and are foods which should be included regularly as part of a healthy balanced diet.
The last thing to take away is that these “negative calorie” foods are typically low calorie. Take the celery for example: It has 5 calories per stick (30g) compared to 30g of chocolate which is 159 calories.
This article was written by our dietitian Rhiannon Welsh who is a nutritionist, Accredited Practising Dietitian and Dietitians Association of Australia member.
If you have any questions about healthy eating, contact your local doctor who will arrange for you to see a dietitian in Sydney. Contact us today!
Bibliography
- Barr SB, Wright JC. Postprandial energy expenditure in whole-food and processed-food meals: implications fpr daily energy expenditure. Food and Nutrition Research. 2010; 54.
- Calorie King. [Online].; 2013 [cited 2013 July 26]. Available from Calorie King Australia
