By comparison with the average 15-year weight gain in participants with infrequent (less than once a week) fast-food restaurant use at baseline and follow-up, those with frequent (more than twice a week) visits to fast-food restaurants at baseline and follow-up gained an extra 4·5 kg of bodyweight and had a two-fold greater increase in insulin resistance.
Fast-food consumption has strong positive associations with weight gain and insulin resistance, suggesting that fast food increases the risk of obesity and type 2 diabetes.A 10 lb difference in weight gain over 15 years may not seem like much, but believe me, for this type of study, that's a massive association. It's a rate of weight gain that would make a lean person overweight in about 30 years.
Fast food, like all industrial convenience food, is professionally designed to maximize reward value and is therefore exceptionally fattening and unhealthy in my opinion. Most studies of this type measure specific dietary components, like fat, carbohydrate, fiber, meat, dairy, and vegetable intake. What those studies miss-- which I think is a critical factor-- is the form in which those nutrients/foods are consumed. This study addressed that by looking directly at the consumption of industrially processed food, and it found a striking outcome.
Lately, I've been collecting data on how the US diet has changed, qualitatively, over the last 200 years or so. I have some graphs that are very telling. I'll be gradually releasing them on this blog and in my upcoming talks. A gentleman named Jeremy Landen, who I'll introduce in more detail later, has been collaborating with me on this. Here's one of my favorite graphs, as a sneak preview. It represents spending on food consumed at home (green), food consumed away from home (blue and red), and fast food (red), as a percentage of total food expenditures:
- 93 percent of food was consumed at home in 1889, and most of that was homemade from scratch.
- In 2009, barely half (51%) of food was consumed at home, the rest was consumed in either full-service or fast food restaurants. Probably a high proportion of what was consumed at home was actually processed food.
- Fast food was not a significant expenditure before 1960, after which it rapidly gained in popularity. Today, fast food accounts for 18 percent of total food expenditures.