Weight creep can strike at any age, but it’s particularly common after 40. A more sedentary lifestyle, the accumulation of bad habits over time and hormonal changes can all play a role in midlife weight gain, experts say.
But a simple food swap can help. It broadly comes down to focusing on “carbohydrate quality” — swapping certain carbs for others, researchers reported Wednesday in The BMJ.
People who limited their intake of added sugar, sweetened drinks, refined grains and starchy vegetables while eating more whole grains, fruits and non-starchy vegetables gained less weight in midlife than their peers who indulged in a sugary, starchy diet.
The link between these habits and greater weight control was particularly strong among women, and people who were overweight or had obesity before making the changes.
“One of the interesting things in our study was that we found that the starch was actually a bigger problem overall than sugar itself,” Dr. Walter Willett, study co-author and professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston, tells TODAY.com.
“Clearly, too much sugar is not a good thing either, but huge amounts of refined starch are even a bigger problem when it comes to weight control.”
Carb sources matter
The study is based on data from more than 136,000 nurses and health professionals who were 65 years old or younger, and regularly shared their medical history and eating habits in a series of surveys starting in the 1970s and ‘80s. They were followed for at least 24 years.
The authors of the present study looked at the participants’ self-reported diets to see how many carbs they were eating from sources including:
- Added sugar and sugar sweetened beverages, such as soda.
- Refined grains, including white flour, white bread and white rice.
- Starchy vegetables, which are “mostly potatoes. That’s the biggest villain,” Willett says. That includes fried, baked, boiled or mashed potatoes. Sweet potatoes, yams, peas and corn are also in this category.
- Non-starchy vegetables, including tomatoes, greens, carrots, broccoli and cabbage.
- Whole grains, such as whole-wheat flour, oatmeal and brown rice.
Weight creep is real
The participants gained an average of more than 3 pounds every four years. Over 24 years, that added up to an almost 20-pound gain, on average.
The participants updated their information every two to four years, so the researchers looked at how self-reported changes in their diet over time affected their weight.
The study found increasing starch or sugar by 3.5 ounces a day was associated with gaining 3 pounds and 2 pounds more, respectively, than the average over four years.
But people who increased their intake of whole grains, fruits or non-starchy vegetables by 3.5 ounces a day saw a smaller weight creep over that time, gaining about 1 pound, 3 pounds and 6 pounds less, respectively, than the average.
Why not just limit all carbs in general and focus on a low-carb diet?
“We actually found that if it’s the whole grain — the less refined kind of carbohydrates — they actually add positive value,” Willett says.
“We get a lot of fiber that way. There are lots of minerals and vitamins and phytochemicals that have positive health benefits. So there’s a good side to healthy carbohydrates and a pretty major negative side to too much refined starch and sugar.”
Choose fiber and ‘slow carbs’
The best carbohydrates are the intact whole grains such as a kernel of wheat or a whole grain of brown rice, he says.
Previous studies have found foods high in fiber may help people lose weight.
Fiber-rich “slow carbs,” found in fruits, vegetables and whole grains, take longer to digest, cause a slower rise in blood sugar and help people feel full.
Refined grains, on the other hand, have been milled, a process that removes the bran and germ, according to the U.S. Department of Agriculture. Many of the micronutrients and much of the fiber is lost, leaving a form of carbohydrate that’s starch, which is rapidly broken down and absorbed when people eat it, Willett notes.
“We get a big burst of glucose and that signals the pancreas to put out a blast of insulin. The insulin drives that glucose into the fat cells, where it’s converted into fat and it’s stored there,” he adds.
“Even though we may be hungry, our body keeps it locked up as fat. That’s not a good outcome.”
Starch from refined grains and starchy vegetables was slightly more strongly associated with weight gain than the same amount of added sugar, the study found.
The findings “raise concerns” about the current recommendation of the Dietary Guidelines for Americans to eat more of all types of vegetables, including starchy vegetables, the authors caution.
“We’re in the middle of an obesity epidemic and you’re recommending more potatoes? It’s really not a good idea,” Willett says.
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