Harvard Study Finds Certain Foods – NOT Calories – Have a Strong Impact on Weight Gains and Losses
Individual foods are more important than calories when it comes to long term weight gains or losses, according to the study. Specifically, potatoes are associated with weight gain, along with sugar-sweetened beverages and meats, while foods like fruits, vegetables, whole grains, nuts and yogurt, are associated with weight loss, according to the study.
“Modest changes in specific foods and beverages, physical activity, TV-watching, and sleep duration were strongly linked with long-term weight gain. Changes in diet, in particular, had the strongest associations with differences in weight gain… The idea that there are no ‘good’ or ‘bad’ foods is a myth that needs to be debunked,” said a researcher in a press release. The study appears in the June 23, 2011, issue of the New England Journal of Medicine.
When I was contacted by USA Today reporter, Oliver St. John, to comment on the Harvard Study, this gave me an opportunity to look over the study so that I could offer an analysis which would help not only “USA Today” readers, but me and my clients better understand it.
I found some of the claims made regarding the study incomplete.
While this is an interesting study and confirms much of what we know about healthy and unhealthy foods, I’m concerned about the sweeping conclusions for the following reasons:
The Harvard study is epidemiological, the kind of study which analyzes large populations and their health outcomes. Because the facts cannot be precisely measured, as it would be in a clinical study -nobody is weighing and measuring the foods people are eating, their body weights, or their lifestyle patterns – the conclusions which can be made are limited. This is true for many reasons. First, there are no “controls” in the study; making it difficult to tease out confounding variables having an effect beyond the particular foods being studied. What I mean is: eating certain foods is associated with specific behavior patterns, so it’s impossible to determine if the effect (weight loss/gain) is due to the food or the behavior pattern. For instance, studies of whole-grain eating find it is a “marker” for engaging in many healthy behaviors. People who eat whole grains are more likely to exercise and eat more vegetables. SO when epidemiological studies find whole grain- eaters are healthier, one must ask: is the effect due to eating whole grains or the lifestyle associated with eating whole grains? The only way to answer this question is, once the epidemiological data is observed, to take the observations into a lab and do a controlled clinical study. The clinical study would need to control for everything – exercise, diet, body weight, etc – and change only whether people are eating refined or whole grains, to determine if the health effect is due to the whole grain eating or the lifestyle.
The Harvard study found potato-eating associated with weight gain. The researchers warned against eating potatoes, attributing the weight gain to the rise in blood sugar caused by potatoes.
I am not quite convinced. Why?
First, many foods cause rises in blood sugar – including whole wheat bread and whole grain cold cereals. But they aren’t associated with weight gain, in fact, quite the opposite.
Second, in America, most potatoes are eaten as french fries or potato chips, and these are very fattening versions of potatoes. So, the way potatoes are cooked – not the potato itself – may be why Harvard’s epidemiological study found potato-eating is associated with weight gain. This argument points to excess calories as a factor.
Also, and this may be an important factor explaining why potatoes are associated with weight gain. When people eat french fries, they are usually eating hamburgers and hot dogs alongside. Not only that, the beverage they’re drinking is SODA (a known contributor to obesity in adults and children). Therefore, instead of the potatoes causing the problem, could it be the meal pattern or high calorie lifestyle associated with people who eat french fried potatoes? In the United States, french fries are eaten together with fattening, unhealthy foods, known to be correlated with increased weight, diabetes, heart disease, you name it. Same with potato chips. People who regularly eat french fries, potato chips, and sodas also eat other fattening and unhealthy foods. In fact, studies show soda-drinking, for instance, is another “marker” but this time, for engaging in unhealthy behaviors like smoking and being sedentary. These confounding variables could influence the study’s results.
This brings me to the last piece of evidence – and what convinces me the most – that potatoes do not a cause weight gain: SWEDEN
In Sweden, people are no fatter than Americans, in fact, they’re slimmer. But, they eat potatoes every day, and often more than once a day. But when Swedes eat potatoes (and I’m sure of this as I am a Swede and visit often), they eat them in small portions, they’re boiled, topped with a little butter (oops), alongside FISH. Not burgers, not fried fish, just grilled, steamed, cured, smoked, or sauteed FISH.
So, if eating potatoes in Sweden is not associated with weight gain, could it be because the potatoes are cooked in a healthier way than in the United States and the meal pattern is a healthier one? 1) the potatoes are boiled, not fried, 2) the potatoes are eaten in smaller, more reasonable portions, and 3) the potatoes are more often eaten together with other healthy foods, such as fish – not burgers and sodas.
And, how do you explain all those poor, skinny Irish and Russians – heck, anyone living in the northern parts of the world – people who subsisted on and depended on potatoes as their only vegetable for centuries. Why didn’t the potatoes make them fat?
Do I believe potatoes are a wonder food? No. But I also do not believe potatoes are “POISON,” as some commentators have stated.
Should you be eating larger portions of watery vegetables and smaller portions of starchy vegetables, such as potatoes? Yes.
Do I occasionally enjoy French Fries and Potato Chips, known to be fattening, unhealthy foods? Yes I do.
Do I eat French Fries and Potato Chips on a regular basis? No, I do not. Do I wish I could?
Yes I do, but I’d rather be healthy and slim.
People eating nuts were more likely to have lower body weights, according to the Harvard Study. Their explanation is that nuts are satiating; they make us feel full, inferring that they lead to eating fewer calories overall. Clinical studies have found years ago that adding nuts to meals, especially breakfast, decreased overall calorie intake, making weight loss easier. This is one reason why I have been encouraging nut-eating for many years. Also, we’ve known for quite a while that nut-eaters around the world have fewer heart attacks and are healthier in other ways.
Does this mean you cannot gain weight eating too many nuts? No. Plenty of people eat too many nuts and can become overweight because of it. Nuts are healthy, but fattening little morsels. One ounce, or a small handful, contains about 180 calories. This is why I recommend most people eat one ounce per day. But if weight is not an issue, two ounces a day – or more, if you can afford the calories, is fine – and is even heart healthy. When I work with people wanting to gain weight healthfully, I advise snacking on nuts!
Are certain nuts better than others? I’m not convinced of this. Every time a new study comes out about a nut – any nut – it’s positive news. Certain nuts, though, are more commonly eaten, have a bigger consumer base, and more money to fund scientific studies. This may be why you hear about some nuts over others. It is also a very expensive and time-consuming process for a food to be approved for a health claim on a food label. So, only certain nut growers can afford to put health claims on their labels, and educate you about their health benefits.
While you already know each nut has a different look and flavor, each nut also has its own unique nutritional characteristics. For instance, almonds are the highest in protein and Vitamin E, and the lowest in artery-clogging saturated fat. Walnuts are the only nut with omega-3-fatty acids. Pecans have the highest antioxidant content. Pistachios contain lutein, a compound which may significantly improve eye health.
Bottom Line: Eat nuts every day.
They’re good for you and may help you eat fewer overall calories because they’re so satiating!
Yes, calories matter: So, stick with just one or two ounces, if weight is an issue. If not, eat more.
The study found yogurt-eating associated with lower body weights. Whole civilizations have known about yogurt’s health benefits for thousands of years.
When my mother was recovering from hip replacement surgery I advised her to live on yogurt, fruits and vegetables for healing AND to prevent weight gain from being immobile. It worked. She healed very quickly and lost a little weight at the same time. She was thrilled. I’ve repeated the same advice to my clients, when appropriate, and they’ve been thrilled with the results, too.
Yogurt has many positive qualities. I’m convinced: Yogurt is a Superfood; it may be one of the best overall foods you can eat. Yogurt creates a natural way to boost your immune system by providing probiotics which increase the healthy bacteria in your gastrointestinal tract, according to my friend and colleague, Jo Ann Hattner, MPH, RD, in her book, “Gut Insight.”
Probiotics are live bacteria that promote digestive health. As we age, it is thought that bacterial populations in our gut change – resulting in increased harmful, disease-causing bacteria and fewer protective bacteria. When you add probiotics you repopulate the gut with beneficial bacteria that protect against infection-causing toxins.
You also improve colon health by lowering pH of the colon, so it’s receptive to the beneficial bacteria and detrimental to the disease-causing bacteria, you protect the intestinal lining, and strengthen immunity. Exciting research is evolving on the health benefits of probiotics.
But correlating yogurt with lower body weights is complicated. Do you believe people who regularly eat french fries, potato chips, burgers and sodas eat much yogurt? I don’t think so. This is another case where lifestyle probably plays a huge role and why Harvard’s epidemiological study found yogurt was associated with lower body weights.
While it may be true that yogurt has health benefits causing leanness, this hasn’t been proven conclusively in clinical studies yet. There have been studies showing dairy foods are very satiating… That is, when you eat yogurt, you feel full in relation to the calories. And when you feel extra satiated by something, such as yogurt or nuts, it helps you eat fewer overall calories for the day. There is some evidence that the protein in yogurt may be especially high quality, spare lean muscle (and bone), and increase metabolism, thereby making weight loss a little easier. Diary products may also contain other bioactive compounds contributing to leanness. The Harvard researchers speculated the probiotics in yogurt may be responsible for the weight benefit. All of these reasons could be significant. But, the most significant factor probably is: Yogurt-eaters are more likely to live a healthy lifestyle, exercise, and eat other healthy foods.
My clients, family and friends have known this for years. Why? I love keeping up with the science and keep myself and them informed.
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