What’s the best way to keep weight off as you age?  The newest research suggests that the conventional weight loss wisdom — to eat everything in moderation, eat fewer calories and avoid fatty food — isn’t the best approach to keeping weight off over the years.

In the most thorough and long-term study about age-related weight gain to date, Harvard University researchers found that the type of foods we eat may have as much impact on weight control as portion sizes.


“People don’t become overweight overnight.  Rather the pounds creep up slowly, often unnoticed, until one day nothing in the closet fits the way it used to” points out Jane Brody, personal health columnist for The New York Times.  “The beauty of the new study is it’s ability to show, based on real-life experiences, how small changes in eating, exercise and other habits can result in large changes in body weight over the years.”

The researchers said the most surprising finding was that yogurt, among all foods, was most strongly linked to weight loss.

And despite conventional advice to eat less fat, weight loss was greatest among people who ate more yogurt and nuts, including peanut butter.

Contrary to what many people believe, an increased intake of dairy products, whether low-fat (milk) or full-fat (milk and cheese), had a neutral effect on weight.

Participants who lost weight consumed 3 more servings of vegetables each day compared to those who gained the most weight.

Alcohol intake had an interesting relationship to weight changes. No significant effect was found among those who increased their intake to one glass of wine a day, but increases in other forms of alcohol were likely to bring added pounds.

“The bottom line here is, the quality of the diet can make a big difference in the long-term ability to control our weight. ”

The foods that contributed to the greatest weight gain were not surprising – Regular consumption of potato chips, French fries and sugared beverages were most to blame for slow and steady weight gain.

Also not surprising  – and consistent with the Harvard study – is the finding by a Boston Children’s Hospital study that metabolism slowed with the consumption of refined grains but stayed the same after consumption of whole grains.

Here are some highlights from a recent interview with Dr. Walter C. Willett, co-author of the Harvard University study about the factors that influence weight gain or loss as we age:

Q. What’s the main message about the study on different foods and their effect on long-term weight gain?

A. The bottom line here is, the quality of the diet can make a big difference in the long-term ability to control our weight.

Q. Yogurt is considered a healthy food, but people who eat it also seem to do better with weight. Could that be a marker for better, healthier lifestyle, or is it something about yogurt?

A.Yogurt was sort of a surprise here. It did come out in all three of the studies that we looked at, that are a part of this report. The yogurt finding does need to be looked at in further detail.

Q. Peanuts and other nuts did fairly well. Why is that? They’re a very calorie-rich food.

A. In this study, and many other studies, it has been found that tree nuts and peanuts as well are not related to higher weight gain. Nuts are very satisfying; calorie-for-calorie, we’re less likely to be hungry three or four hours down the road than if we were eating some other type of food. In the long run, it can add up to less weight gain.

Q. What is the biggest bill on American diets?

A. Sugary beverages — sodas, sports drinks — were among the top contributors to weight gain. They are a special problem because so many people consume multiple servings of sugary beverages on every day. That makes them the number one problem related to weight gain.

Q. And it seems orange juice is not that much better in terms of weight control than sugared beverages. There’s this whole idea that juices are healthy. How do you deal with that in terms of public health recommendations?

A. People have been given the idea that fruit juices are a really healthy choice, but, in fact, fruit juice has just about the same number of calories as a full-sugar soda. And it’s just as easy to over-consume fruit juice just as it is to over-consume regular soda.

Q. Let’s take the worst of the study: potato chips. Do more people who tend to eat potato chips tend to be junk food eaters in general, or is it that potato chips tend to be practically bad?

A. On average, people who ate more potato chips tended to eat other unhealthy things in the diet. But we looked at that pretty carefully and adjusted for those other factors — and, still, potato chips held up on their own.

Q. The study shows that eating potato chips cause weight gain and yogurt tends to [lead to] weight loss. Can you explain why you don’t worry about portions? If you ate a bucket of yogurt and one potato chip, clearly, they would have different effects on your body.

A. Certainly, paying attention to portions sizes makes sense. But, also, it is pretty clear that the kinds of foods we eat make it harder or more difficult to control our caloric intake.  Maybe you’ve heard the line that ‘you can’t stop after eating just one,’ and that’s part of the problem with potato chips.

Q. This study will be seen mostly about types of foods that affect weight gain, but I presume this is because you controlled for the exercise and the other life style factors?

A. We found that more [exercise] was related to less weight gain. We also looked at television and watching TV was related to more weight gain.  Both physical activity and diet are important to weight control, but if you are fairly active and ignore diet, you can still gain weight.

To read more of Dr. Willet’s interview, click here: For weight control, it’s what we eat that counts.