Nuts, Fat, Added Sugars: New Research

By Kathleen Doheny
WebMD Health News

Reviewed by Michael W. Smith, MD

March 6, 2015 -- Whether you're young or old, it's a good idea to cut back on fat and added sugars and eat more nuts. That's according to three new studies, which say those habits may help you stay healthy, and lose pounds or maintain your weight. The studies were presented at the annual meeting of the Endocrine Society.

For starters, teens who eat a modest amount of nuts daily have a lower risk of getting metabolic syndrome, says researcher Roy Kim, MD, MPH. Metabolic syndrome is a cluster of conditions, such as high blood pressure and high blood sugar, that raises the risk of heart disease and diabetes.

Kim is an assistant professor of pediatrics at the University of Texas Southwestern Medical Center. His team studied data on the nut-eating habits of more than 2,200 young people, ages 12 to 19.

Those who ate about a half-ounce daily were healthier, Kim found, than those who did not. They had a lower body mass index (BMI), a smaller distance around the waist, slightly more "good" HDL cholesterol, and lower blood pressure, he says.

Fewer than 9% of the teens ate that many nuts a day, Kim says, and more than 75% ate no nuts at all. "Those eating a lower amount of nuts per day (less than a half-ounce) had more than a doubling of metabolic syndrome" compared to those eating a half-ounce or more a day.

A half-ounce adds up to about 12 almonds, 14 peanuts, or seven walnut halves.

The same link between nuts and a lower risk of metabolic syndrome has been found in adults, Kim says.

Low-Fat vs. Low-Carb Diet

For years, the diet pendulum has swung back and forth, with experts recommending low-carb diets for optimal weight loss, then suggesting low-fat diets, and then back again. Carbs and fat have been taking turns at being ''the evil nutrient," says Kevin D. Hall, PhD, senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases.

But in his small study of 10 obese men and 9 obese women, average age 24, he found that following a low-fat diet led to about a 67% greater body-fat loss than following a low-carb plan.

The men and women in the study were patients at a metabolic ward, so their food was strictly controlled and their exercise was tracked.

They ate a diet that was 50% carbohydrates, 35% fat, and 15% protein for 5 days. For the next 6 days, they were randomly told to eat either a reduced-fat or a reduced-carbohydrate diet.

"We cut 30% of calories, selecting from carbohydrate or fat," Hall says.

For fat burning, the low-fat diet worked best, Hall found. But it's unknown whether the approach would also work for those who are overweight but not obese.

Eat Less Sugar

Having too much added sugar, especially fructose, has been linked not only to weight gain, but to a buildup of liver fat, in turn boosting the risk for type 2 diabetes and heart disease -- even in teens.

Fructose is a natural part of fruit. But it's also added to many foods and drinks, sometimes as high-fructose corn syrup.

Obese teens who restricted how much fructose they ate, without reducing total calories, were able to lessen the buildup of fat in their liver, says Jean-Marc Schwarz, PhD, a professor of biochemistry at Touro University California.


According to the USDA, there is no difference between a “portion” and a “serving.” See Answer

Schwarz's team studied 40 obese Latino and African-American children, ages 9 to 18, who had regularly eaten high-sugar foods. For 10 days, the children ate only the meals provided, which substituted other, healthier carbs for sugars.

Next, the researchers measured the conversion of sugar to fat in their livers. After 10 days of restricting fructose, the change-over of sugar to fat declined by more than 40%, and liver fat declined by more than 20%, Schwarz says.

The results suggest the liver fat buildup ''can be reversed just by taking away the fructose from the diet," he says.

Guidelines from the World Health Organization recommend you limit ''free'' sugars, such as glucose and fructose, to less than 10% of your daily calories. Under 5% is even better. That translates to about 6 teaspoons of sugar a day. (A can of sugar-sweetened soda has about 10 teaspoons, by the way.)

The guidelines don't refer to sugars found in fruits, vegetables, and milk. They're talking about sugar that's added to foods, such as cookies and pies, and those found in fruit juice concentrates and honey.

Still, studies have shown that cutting back on all types of sugar has health benefits.

Take-Home Points

While some of the findings require more study, some of the diet suggestions are worth following now, says Ann Nardulli, PhD, a physiology professor of at the University of Illinois Urbana-Champaign.

"Nuts would be the easiest," she says. One recent study showed that regularly eating nuts, including peanuts and peanut butter, lowered the risk of early death from heart disease by about 20%.

Cutting back on foods and drinks that have fructose would also be ''a step in the right direction," Nardulli says.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

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SOURCES: Ann Nardulli, PhD, professor of molecular and integrative physiology, University of Illinois Urbana-Champaign. Jean-Marc Schwarz, PhD, professor of biochemistry, Touro University California, Vallejo; associate research endocrinologist, University of California San Francisco. Roy Kim, MD, MPH, assistant professor of pediatrics, University of Texas Southwestern Medical Center and Children's Health, Dallas. Kevin D. Hall, PhD, senior investigator, National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health, Bethesda. ENDO 2015, March 5-8, 2015, San Diego. JAMA Internal Medicine, March 2, 2015.

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