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Harvard Reviews of Health News

Study Finds Chips Pack on Pounds

Potatoes, especially chips, are the biggest cause of gradual middle-age weight gain, researchers said based on a new study. Their analysis included more than 120,000 people from 3 long-running studies of health professionals. They were asked regularly about what they ate and how much they weighed. In 20 years, the average person gained nearly 17 pounds. Researchers said food choices contributed most of that. Potato chips did the most damage. People gained about 1.7 pounds every 4 years for each ounce of potato chips they consumed daily. Non-chip potatoes added 1.3 pounds in 4 years for someone who ate a daily serving. French fries were the biggest culprit within this group. The weight gain was about 1 pound for someone who drank a soda daily and 0.4 pounds for sweets or alcohol. The New England Journal of Medicine published the study. The Associated Press wrote about it July 23.

What Is the Doctor's Reaction?

Maintaining a healthy body weight is more than the simple formula — match calories in to calories out. Recent research tells us a new story. Some foods and beverages cause more weight gain regardless of their calorie counts.

The England Journal of Medicine published the study this week, Harvard researchers looked at results from 3 separate long-term studies. They included a total of 120,877 men and women.

Researchers gathered information about diet, lifestyle choices and changes in weight. The studies included large numbers of nurses, doctors and other health professionals. They were not obese and were generally healthy when they entered the studies.

The researchers evaluated each person over four-year intervals. Weight, history of eating habits, and lifestyle habits were recorded at the beginning of the study. They also were recorded every four years.

The average weight gain for everyone in this new study was 0.8 pounds per year (over 4 years).

I would have predicted sugar-sweetened drinks as the cause of the greatest weight gain. They came in second. Potatoes got top honors, especially potato chips. Red meats and processed meats were also linked with weight gain, compared with other foods and drinks.

The good news is that certain foods are linked with losing weight. These include:

  • Yogurt

  • Nuts

  • Fruits

  • Whole grains

  • Vegetables

Yogurt was a surprise. Of all the foods and beverages, eating yogurt was linked with the least amount of weight gain. My bet would have been on vegetables.

Other lifestyle habits also were linked with greater weight gain. They included:

  • Alcohol use

  • Television watching

  • Getting less than six hours or more than eight hours of sleep per night

But the amount of weight gain in people with any of these habits was nowhere close to that among regular potato eaters.

What Changes Can I Make Now?

As expected, being physically active had the most influence on limiting weight gain. Your minimum should be 150 minutes of moderate intensity exercise every week. This means about 30 minutes most days of the week.

For many people, especially those who have desk jobs, this won't be enough to hold back weight gain. Shoot for a goal of 60 minutes of exercise at least 4 times per week.

Moderate intensity exercise means keeping your heart rate at 60% to 75% of your maximum heart rate. An easy way to calculate maximum heart rate is 220 minus your age.

Other than potatoes, the foods and beverages to eat and drink sparingly were well known. And you don't need to stop eating potatoes. Just limit how much you eat.

For starters, don't include potatoes in your list of vegetables when you shop for groceries. The potato acts like pure sugar in your body. In fact, the potato can increase blood sugar levels just as quickly as an equal amount of calories from table sugar. French fries and potato chips do the same thing, but with an added blast of fat.

We don't know why eating yogurt should be linked with the least amount of weight loss. There is no good biological explanation for this. I suspect that yogurt eaters already tend to watch their weight more closely or are making a real effort to lose weight. So it may not actually be the yogurt that helps to control weight. Some undiscovered factor may be the cause instead.

What Can I Expect Looking to the Future?

We are finally learning about how different foods act in our bodies. This is timely because of the very rapid rise in the number of obese people in recent years. This increase can't be explained solely by increased calorie intake and less exercise.

Certain foods and drinks have greater effects on how fast blood sugar levels rise. Rapid increases in blood sugar stimulate the pancreas to put out more insulin. This cycle leads to weight gain.

It's time to take action on this theory. Even if the blood sugar spike and insulin response are not the major cause of the obesity epidemic, they surely are contributing factors.

Author: Howard LeWine, M.D.
Date Last Reviewed: 6/24/2011
Date Last Modified: 6/24/2011