The Potato Chip Study

Study confirms links between specific foods and weight loss or gain

By Jacob Schor, ND, FABNO

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Reference

Mozaffarian D. Tao Hao PH. Rimm EB.Willett WC. Hu PH. Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011;364(25):2392-2404.

Design

A prospective investigations looking at the relationship between changes in lifestyle factors and weight change. Participants were evaluated at 4-year intervals, with multivariable adjustments made for age, baseline body mass index for each period, and all lifestyle factors simultaneously.

Participants

120,877 U.S. people including 22,557 men, who were free of chronic diseases and not obese at baseline, were followed in this study. They were enrolled in 1 of 3 separate cohort studies, either the Nurses’ Health Study (NHS), the Nurses’ Health Study II, or the Health Professionals Follow-up Study. The follow-up periods were from 1986 to 2006, 1991 to 2003, and 1986 to 2006. This yielded 1,570,808 person-years of follow-up data to analyze.

Lifestyle Factors

The dietary factors assessed included fruits, vegetables, whole grains, refined grains, potatoes (including boiled or mashed potatoes and French fries), potato chips, whole-fat dairy products, low-fat dairy products, sugar-sweetened beverages, sweets and desserts, processed meats, unprocessed red meats, fried foods, and trans fats.

Also evaluated were nuts, 100% fruit juices, diet sodas, and subtypes of dairy products and potatoes. Time spent watching television, types of alcohol drinks consumed, and time spent exercising were also evaluated. Positive and inverse associations were calculated for each cohort and expressed as age-related change or multivariable associated change. The effect on weight of consuming specific foods was more pronounced when the only variable analyzed was age. Analyzing multiple variables blunted the effects, yet they were still significant.

Outcome Measures

Weight gain associated with increased consumption of specific foods.

Key Findings

Average weight gain was 3.35 lb during each 4-year follow-up period or a weight gain of 16.8 lb over a period of 20 years. Increased or decreased consumption of specific foods was associated with either weight gain or weight loss over each 4-year period. These effects can be expressed both as age adjusted change in pounds or multivariable adjusted change in pounds. The later calculations are usually less dramatic as the multiple variables tend to blunt the calculated effect. The abstract and discussion use the values calculated for multivariable adjusted changes. For the point of discussion with patients, using the age adjusted change results may make a greater impression. Below is a simple chart of the data.

Food: Increased Dietary Intake

Weight change within each 4-year period

  Age Adjusted Change

lb.

Multivariable Adjusted Change

lb.

Fruit -0.69 -0.49
Vegtables -0.25 -0.22
Nuts -0.78 -0.57
Whole-fat dairy +0.25 +0.10
Butter +0.47 +0.30
Cheese +0.13 +0.02
Low-fat yogurt -1.16 -0.82
Potato chips +3.01 +1.69
Potatoes +2.14 +1.28
French fried potatoes +6.59 +3.35
Whole grains -0.59 -0.37
Refined grains +0.56 +0.39
Sugar-sweetened beverages +1.32 +1.00
Sweets or desserts +0.65 +0.41
Processed meat +1.76 +0.93
Trans fats +1.44 +0.65

The largest positive associations with weight changes were seen for consumption of potatoes. For example, consuming a serving of potato chips each day apparently leads to a 1.69 lb weight gain over a 4-year period. French fried potatoes were far worse, leading to a 3.35 lb weight gain.

Inverse associations, that is weight loss per serving consumed, were seen for a number of foods. The most dramatic effects were seen in those who added yogurt and nuts into their diets. Daily consumption of nuts was associated with slightly more than half a pound of weight loss (-0.57 lb) over a 4-year period, and yogurt a -0.82 lb loss. These were all linear relationships for both increased or decreased consumption. That is, the weight change seen for increased consumption reversed along the same line if consumption decreased. For example, eating more French fries was associated with increased weight while eating less was associated with weight loss.

Less weight gain occurred with decreased consumption of potato chips, processed meats, sugar-sweetened beverages, potatoes, or trans fat, and more weight gain occurred with decreased consumption of vegetables, whole grains, fruits, nuts, or yogurt.

Thus, less weight gain occurred with decreased consumption of potato chips, processed meats, sugar-sweetened beverages, potatoes, or trans fat, and more weight gain occurred with decreased consumption of vegetables, whole grains, fruits, nuts, or yogurt.

The length of time participants slept on average each night yielded a U-shaped association with weight gain; people who slept less than 6 hours or more than 8 hours gained more weight. An additional hour watching television led to a weight increase of 0.31 lb. Those participants who quit smoking experienced a weight gain of 5.17 lb during the first 4-year period in which they quit, but after that initial gain, the former smokers gained only 0.14 lb in the following 4-year period.

Practice Implications

Mozaffarian and colleagues have published a series of fascinating studies on eating patterns and health over the past years. For example their papers on fish consumption and heart failure, and especially the relationship between fried fish consumption and increased risks, should be changing the way we counsel patients. This paper is different. For naturopathic physicians, the information is just so much preaching to the choir. This study only confirms what we have believed for years and changes little, if anything, in our practices. We already teach our patients to eat more vegetables, fruits, nuts, whole grains, and yogurt. We tell them to avoid simple carbohydrates, sugars, refined grains, and desserts. We especially tell them to avoid regular consumption of fried simple carbohydrates like French fries and potato chips. Certainly having these numbers to present to our patients from such a reputable source lends strength to our message, though it does not change it.

These data squash the notion that weight gain or loss is a simple equation of caloric intake versus energy expenditure. Weight gain or loss is more complex, and increased consumption of ‘healthy foods’ and avoidance of bad foods, especially potatoes, leads to weight loss. This concept is not new to any of us. Simple carbohydrates increase weight gain.

Perhaps the most important thing about this study is that the food and weight change lists—and especially the graphic charts that sum up these data—may become effective tools for educating patients.

A pdf of the study is posted at www.foodpolitics.com/wp-content/uploads/NEJMoa1014296.pdf

About the Author

Jacob Schor ND, FABNO, is a graduate of National College of Naturopathic Medicine, Portland, Oregon, and now practices in Denver, Colorado. He served as president to the Colorado Association of Naturopathic Physicians and is on the board of directors of the Oncology Association of Naturopathic Physicians. He is recognized as a fellow by the American Board of Naturopathic Oncology. He serves on the editorial board for the International Journal of Naturopathic Medicine, Naturopathic Doctor News and Review (NDNR), and Integrative Medicine: A Clinician's Journal. In 2008, he was awarded the Vis Award by the American Association of Naturopathic Physicians. His writing appears regularly in NDNR, the Townsend Letter, and Natural Medicine Journal, where he is the Abstracts & Commentary editor.