If they had to guess which foods they eat that most contribute to weight gain and that keep them from losing weight, most people would include french fries and potato chips on the list. Well, a long-term study that is the first to look at weight gain and loss and associate it with individual foods says that they'd be right.
This study, recently published in The New England Journal of Medicine, follows the lives of over 100,000 men and women over a 20-year period. It found that during that period the average weight gain by participants was 17 pounds, or 3.35 pounds per year. Evaluating patient data in four-year increments, the researchers also tracked how much of that weight gain was caused by specific foods. Potato chips were the "winner," associated with an average weight gain of 1.69 pounds, followed by potatoes in general at 1.28 pounds. (French fries caused even more weight gain, naturally, because of the amount of fats used to cook them.) Lead study author Dr. Dariush Mozzafarian believes that this could be because potatoes contain refined carbohydrates and starches that cause spikes in the glucose and insulin levels in our blood. These spikes then cause the perception of hunger, and cause us to increase the amount of food we eat at the next meal.
Some foods linked to weight gain, others to weight loss
Other culprit foods tied to weight gain included sugary beverages such as colas, which accounted for an average 1.0 pound of weight gain over four years. Eating unprocessed meats resulted in a 0.95 increase in weight over the same period, followed closely by processed meats, which caused a weight gain of 0.93 pounds. Drinking alcohol caused a 4-year weight gain of 0.41 pounds.
But it's not all bad news. The study also found links between certain foods and weight loss over the same four-year intervals. For example, subjects who regularly ate yogurt lost 0.82 pounds, and those who ate nuts showed an average four-year loss of 0.57 pounds. Similar losses were seen in those who changed their dietary habits. Those who added a daily serving of fresh vegetables to their diet lost an average of 0.22 pounds, and those who added whole grains lost almost 0.37 pounds. The largest average weight losses were seen in those who added fresh fruits to their diets; they lost an average of 0.49 pounds over four years.
The study authors attribute the weight loss to the fact that fruits, nuts, vegetables, and whole grains – while they contain calories of their own – tend to cause people to eat fewer "calorie-dense" foods such as potatoes and meats. They also contain more fiber, which may make them more satisfying, in terms of feeling full or satiated. The "weight gain" foods such as potato chips and colas and meats tended to be less satiating and filling, and triggered hunger signals that caused people to overeat at the next meal.
Weight loss wasn't all the result of eating the right foods
The study also found hard evidence that the warnings of researchers about the bad effects of inactivity and living a sedentary lifestyle are well-founded. Among the study participants, those who watched an hour of TV every day gained 0.31 pounds during each four-year period. They also tended to snack more while watching TV, which added even more to their weight gain. The amount of sleep participants got was also a factor; those who got between 6 and 8 hours of sleep a night were much less likely to gain weight than either those who got less than 6 hours or more than 8 hours of sleep a night.
Hopefully these findings will be of use to you in keeping your weight under control, or losing weight if you need to. They're not really "Breaking News" in that they reflect what nutritionists and doctors have been telling us for years – eat more fresh fruits, nuts, and vegetables, get more exercise, and get enough (but not too much) sleep. And lay off both the TV and the potato chips you used to eat while watching it.