A little insight…
Are you familiar with NSP’s? NSP is short for non-starch polysaccharides, these are complex carbohydrates that are present in the food we eat. Polysaccharides have at least 10 sugars connected together, but can even have up to several thousand sugars in one chain. This is extremely high when you compare this to monosaccharides (simple sugars) such as table sugar, which only contain 1 or 2 units of sugar, and complex carbs such as starches like pasta, potato or rice which have 3 or more sugars.
Calories & chemical structure
The complex structure of polysaccharides make them difficult for the body to break down. Now although starchy carbs are in fact polysaccharides too, our bodies have the required enzymes needed to break them down. However, non-starch polysaccharides don’t have the necessary enzymes to break their sugar bonds, hence non-starch polysaccharides are more commonly known as FIBRE.
Fibre is the main reason YOU are consuming more CALORIES than you think. Current food labels do not factor in soluble fibre, even though soluble fibre is known to contain approx. 3-4 calories, whereas insoluble fibre (the type our bodies struggle to digest) delivers practically 0 calories. It is for this reason that calories are thought to be underestimated in many foods by as much as 25%!
Time to shake things up a little
Researchers believe that food calorie allocation and labelling needs a major overhaul, Professor Wrangham insists (for obvious reasons) that it is imperative that the consumer has the correct information about what they eat. Not knowing the total calorie content of certain foods can implicate weight and total health, the implications extend above and beyond ‘a right to know for knowing’s sake’, there are actually very real health and medical implications attached too.
Calories miscalculated in both directions
It seems that calories are not just underestimated too, you may or may not have seen my quick post on ‘How we are actually overestimating the calories in nuts’? If you missed it, I was basically explaining how the calories that are listed on a packet of nuts may be approx. 25% higher than the calories you will actually absorb from the food. Click the link above to see how and why this is.
If we were to stick food into a bomb calorimeter (a device that measures the calories in food) then we would get a pretty good idea of how many calories there are in a given food. However, total calories and metabolised calories are two different things because the breakdown of food see’s you lose some calories during the digestive process. This occurs because of the energy cost of digestion, and the fact that your body isn’t always able to digest every cell in the food.
Some calories go straight through us
Nuts are a prime example of overestimating the calories in food, our digestive tract is unable to breakdown every cell in the nut meaning we do not absorb every calorie. The calories in vegetables are also overestimated because raw veg provides less calories than cooked due to the structural integrity of the sugars when raw (not able to digest all sugars). The digestion involved in breaking down the fibres in veg comes at a greater energy cost to the body, meaning your net calorie absorption is lower than stated. The difference can be as much as 10-30% in fact!
The current EU legislation is reliable and robust, however it needs to be reassessed in order to account for the discrepancies mentioned…and fast! Don't get me wrong, fibre is phenomenally important from a health perspective, heck, many nutritional supplements are fortified with fibre (has fibre added to them) in order to 1.) increase the transit rate of fat through the bowl, meaning you absorb less of it, and 2.) satiate you i.e. make you feel fuller for longer. See examples of these weight management supplements HERE
Block, J, P., Condon, S, K., Kleinman, K., Mullen, J., Linakin, S. (2013). Consumers’ estimation of calorie content at fast food restaurants: cross sectional observational study. Retrieved 28th July, 2015, from http://www.bmj.com/content/346/bmj.f2907
Chandon P, Wansink B. Is obesity caused by calorie underestimation? a psychophysical model of fast-food meal size estimation. Journal of Marketing Research2007;44:84-99.
The Guardian, (2013). Food labelling underestimating calorie content of some foods, scientists say. Retrieved 28th July, 2015, from http://www.theguardian.com/science/2013/feb/18/food-retailers-underestimating-calorie-content