Junkfood add weight
What do we call foods composed mostly of sugar and saturated fats, with no real nutrients to speak of? Ultra Processed Foods (UPF) is an attempt at neutral naming, but Junkfood is actually a very fair description of these worthless or even harmful foodstuffs, with their potentially heavy impact on cardiovascular health.
But this post on Junkfood is not about what it does to your heart and arteries, it’s about what it does to your body weight.
You probably feel, intuitively, that all that fat and sugar mean a lot of calories, and you know that excess calories translate into body weight. But then again, all foods contain calories. There are even some Healthy Foods, such as avocadoes and almonds, which actually contain large quantities of calories. And calories in fruit come entirely as fructose, a monosaccharide. So, all calories being equal, your scales couldn’t be showing any difference between Junk and Healthy Food. Or could they?
Actually, they can. Or rather, there is some trickery going on.
This trickery has been exposed in an elegant experiment by professor Kevin Hall and his co-workers (1). They set up a study in which 20 adults (10 men and 10 women) spent four weeks in a metabolic unit. A metabolic unit is a closed living environment in which both dietary intake and energy expenditure can be monitored exactly throughout the study. The participants were chosen for a stable body weight and slight overweight before the study. During the study, they received two different diets in succession, for 14 days each, in random order. One diet was based on ultra-processed foods, the other on minimally processed foods.
The two diets contained exactly the same quantities of calories, sugar, fat, fibre and protein. But after consuming their standard portion, the participants were free to ask for more.
And what happened?
The participants consumed 500 calories more per day on the ultra-processed food diet than on the “normal” diet; and 500 calories is huge. Their body weight rose in proportion to the energy intake, and their blood parameters altered.
Professor Hall has said in an interview (2) that it seems probable that this overeating is a result of the impact of the ultra-processed food diet on the hormones which signal hunger and satiety.
If our health authorities decided to apply the precautionary principle to junkfood as strictly as they did in the matter of “mad cow disease” in the 1990’s, Instructions for Use would be mandatory with all ultra-processed food. These foods which have a very serious effect on our neurobiological hunger and satiety signals, they blunt our ability to regulate our food intake ourselves. Therefore, it will not do to count on individual willpower alone to stave of obesity.
In short, beware of junkfood.
This post is taken in part from my book «Changer de poids, c’est changer de vie», published in March 2020. More info here.
(1) Hall, K. et al. Cell Metab 2019 doi : 10.1016/j.cmet.2019.05.008
(2) Nutrition Action Healthletter. July/August 2019, p 3–6
2Nutrition Action Healthletter. July/August 2019, p 3-6