Potatoes Lead to Increased Weight Gain: Results of a New Harvard Study

by Allison Knott

A recent study from the Harvard School of Public Health, published in the New England Journal of Medicine, found a relationship between potato and French fry consumption and weight gain.  The study, released in the June 2011 issue of the journal, took data from the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study.  Each cohort was analyzed for diet, physical activity and smoking habits and their relationship with weight gain over four year periods.

Conclusions from the cohort study indicated a relationship between certain lifestyle factors, such as smoking and average amount of sleep per night, as well as specific dietary patterns related to weight change over time.  For example, individuals who increased television viewing gained 0.31 pounds per hour of TV watched.  In addition, sleeping less than six hours and more than eight hours per night was also associated with weight gain over time.

In addition to lifestyle factors, dietary patterns were also analyzed and specific foods were pinpointed as contributors to weight change over time.  Potatoes, including French fries, potato chips and baked potatoes, were found to contribute to the greatest weight increase.  Potato chip intake was associated with a 1.69 pound weight gain while potatoes contributed to a 1.28 pound weight gain.  Sugar sweetened beverages, unprocessed red meats, and processed meats were not far behind with a 1.00 pound, 0.95 pound, and 0.93 pound weight gain, respectively.

However, there was an inverse relationship between the intake of vegetables, whole grains, fruits, nuts, and yogurt and weight gain in the cohort.  This inverse relationship increased as each serving of the foods contributing to weight loss, increased.  So, as individuals ate more food from this group, he/she lost more weight.  This finding led the researchers to discuss the possibility that their increased consumption may displace the intake of other foods that contribute more calories, possibility due to the higher fiber content.

The study did not analyze total calorie intake because of the potential inaccuracies a dietary questionnaire can present as well as the questionnaire’s inability to represent caloric balance.  The researchers concluded that there is a “divergent relationship between specific foods or beverages and long-term weight gain, suggesting that dietary quality (the types of foods and beverages consumed) influences dietary quantity (total calories).”

The study challenges the idea that total calories consumed is the key to weight control and that the type of food does not matter.  It is noteworthy because it points to specific foods that lead to weight gain.  However, it should be noted that the researchers state a calorie increase of 50 to 100kcal per day overtime can lead to unintended weight gain, despite the food source.  But with their findings, the researchers suggest that in order for weight loss to be effective, specific foods must be targeted for a decrease or increase in consumption amongst the population.

Allison Knott has been a registered dietitian since 2008 and was previously employed in a hospital in Georgia.  She is currently pursuing a master of science in Nutrition Communication.  Her passion is to communicate accurate and sound nutrition information to the general public. She also blogs at choiceshabitslifestyle.com.

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