Quality calorie vs empty calorie: what’s the difference?
The British Nutrition Foundation (BNF) recently announced a new concept in a press release – the ‘quality calorie’. The purpose of this concept is to highlight the importance of the quality of the foods we are eating, rather than focusing solely on calorie quantity.
Does this mean that calorie quantity is no longer a significant factor? According to the BNF, not exactly; they maintain that the quantity is still important. Ayela Spiro, Science Manager at the BNF, had this to say:
“In order to help battle the obesity crisis, it is, of course, important to be aware of the calories we eat and drink, but we also need to be mindful of the nutritional quality. We need to think about both the quantity and quality of calories”
Nevertheless, this appears to be a slight shift away from the typical calorie-counting or ‘energy balance’ paradigm we hear so much about, which assumes eating less and moving more is the one and only way to lose weight and improve health. Why then, is it so important to look at the quality of our calories?
Nutrient density and empty calories
When concentrating solely on reducing calorie intake, which usually involves eating low calorie products, the nutrient density of foods can often be overlooked. There are many nutrients required for optimal health and processed, low calorie foods can often be lacking in these, instead containing added sugars and other additives to improve their palatability. The lack of nutrients offered by these products makes their calories ‘empty calories’, and the few nutrients they do provide are usually added rather than being natural to the product.
Ultra-processed foods provide around 58% of calories in the standard American diet (that’s a lot of empty calories) and it is likely a similar story in the UK. But, as the concept of the quality calorie would imply, focusing instead on eating fresh, real, unprocessed, nutrient-dense foods can offer better nutritional ‘bang’ per calorie ‘buck’. For example, an avocado contains more calories than a cookie, due to its high healthy fat content, but while the avocado is packed full of natural vitamins, minerals and phytonutrients, the cookie of course is not. Unprocessed foods such as fresh fruit and vegetables, meats, dairy products, nuts and seeds contain a range of essential nutrients, making them quality calories.
Calories in, calories out (CICO)
It is often said that in order to maintain a constant weight, calories in must equal calories out, or put another way, to lose weight, one must be at a calorie deficit. On this note, the obesity epidemic is often blamed solely on the assumption that people are eating too many calories and not doing enough exercise – hence the ‘eat less, move more’ mantra. But does this view hold any real merit?
As we’ve highlighted before, one issue with the CICO model is that it assumes resting metabolic rate (RMR) stays constant during calorie restriction to allow weight loss. This assumption is, however, incorrect. Evidence suggests that long-term calorie restriction can in fact reduce RMR and keep it low, meaning the body puts less energy into normal bodily processes. Burning less calories at rest not only leaves people feeling tired, hungry and cold, but it also makes it harder to lose weight and can even lead to weight regain, which is what is seen in many calorie restriction diet studies.
The key to losing weight and maintaining it in the long term is keeping a healthy metabolism, and diet is instrumental in this. For example, a well-formulated low carbohydrate diet is thought to protect against weight regain due to its sustainable and metabolically healthy nature.
The take-home message
The BNF’s new quality calorie concept is much more in keeping with the evidence base than the typical ‘eat less, move more’ or calorie quantity approach, in terms of achieving and maintaining weight loss and metabolic health.
A real food, low carbohydrate approach, as advocated by our own Low Carb Program, is one strategy for keeping metabolism on-side during weight loss or maintenance. Thinking more about what we eat, rather than how much of it, may well prove important for tackling the current obesity and diabetes crises both in the UK and worldwide.