Are Some Foods Fattening?

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Harvard researchers analyzed prospective data from three cohort studies that followed more than 120,000 initially normal-weight men and women for many years looking for what specific foods and other lifestyle factors might be related to weight gain. In what could be interpreted as a serious challenge to the long held mantra of mainstream weight loss counseling that says, “all foods can fit” into a weight loss diet, the results of this study showed that the consumption of some foods was correlated with increased weight gain. And the consumption of other food items was associated with weight loss.

Food items associated with weight gain could be said to provide less satiety per calorie than foods associated with weight loss. Or more simply, some foods appeared to promote weight gain and could be called “fattening”, while other foods associated with weight loss could be viewed in lay terms as “slimming.” The results of this study showed that on average the subjects gained 3.35 pounds every 4 years so it is pretty clear that most subjects had been consuming a lot more of the fattening foods than the slimming foods. Foods items most closely associated with weight gain were:

• Potato chips (1.69 pounds)

• Potatoes (1.28 pounds)

• Sugar-sweetened beverages (1.00 pounds)

• Unprocessed red meats (0.95 pounds)

• Processed meats (0.93 pounds)

Other food items associated with weight gain included butter, refined grains, sugar-containing drinks, and sweets and desserts.

By contrast, each serving of nuts, whole grains, fruits, vegetables, and yogurt consumed were all associated with a modest reduc- tion in body weight. In addition to diet, the researchers found that several other lifestyle factors were also correlated with weight gain or loss. Not surprisingly those who reported more physical activity either lost weight or were less likely to gain (mean of -1.76 pounds) while those who quit smoking were more likely to have gained weight (mean of 5.17 pounds) over the ensuing 4 years. Each alcoholic drink con- sumed on average per day was associated with a gain of 0.41 pound while each hour per day of TV watching was associated with an average weight gain of 0.31 pound over the ensuing 4 years of follow-up.1

Dr. Mozaffarin’s study results, for the most part, seem fairly consistent with data from clinical trials, which show that certain foods and drinks tend to promote weight gain when consumed ad libitum. For example, most studies show consuming more potato chips, French fries, fatty red and processed meats, refined grains, and sugar-rich foods and drinks would be associated with an in- creased ad libitum calorie intake and weight gain.

Why? Such foods provide less satiety per calorie so while they may taste great they are also less filling. Those with the traditional mind set of limiting portion sizes and counting calories may be puzzled as to how the consump- tion of more whole grains, fruits, and vegetables could lead to weight loss over time.

However, if one focuses instead on eating foods that provide more satiety per calorie it is easy to see how eating foods that are more filling (provide more satiety/ calorie) can actually promote weight loss. How? Because such foods eliminate hunger with a lower calorie cost than one would have to “pay” if they consumed less satiating/calorie or more fattening foods. Even so this was a population study not a clinical trial. It certainly does not prove that dietary advice to eat more nuts or yogurt would aid weight loss or keep people thinner over time. Indeed, when researchers at Purdue University gave a group of normal weight (BMI=23.3) subjects peanuts and instructed them to consume 5 ounces of peanuts daily for the next 8 weeks with no other dietary advice these subjects gained an average of 2.2 pounds.2 If that rate of weight gain were to last for 4 years (not likely) the subjects would have gained an average of 57 pounds. In general research shows foods that have a high calorie density, are high in fat, and have little fiber/calorie provide less satiety/calorie and so tend to be fattening. Given the fact that peanuts and tree nuts are high in fat and very calorie dense with a fairly low fiber/calorie content it would be surprising if advice to consume more nuts would actually aid weight loss.

Bottom Line:

Dr. Mozzafarin’s study suggests that perhaps it is time to change the focus of dietary advice to control weight away from simply counting calories and towards consuming fewer fattening foods and eating instead more foods that provide the most satiety/ calorie. Such an approach may allow people to better control their weight in the long term without trying to micromanage their daily calorie intake by trying to keep track of everything they are eating.

By James J. Kenney, PhD, FACN

References: 1. N Engl J Med 2011;364:2392-

404 2. Int J Obesity 2002;26:1129-37

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