Athens, Ga. - A diet that includes higher amounts of polyunsaturated fats, found in foods like walnuts and salmon, can help offset the detrimental effects of the occasional meal high in saturated fats, University of Georgia researchers have shown in a small clinical study.
They found that study participants who consumed a high polyunsaturated fat diet for seven days showed better fat burning and significant decreases in total cholesterol, among other benefits, compared to a control group that consumed a standard American diet that is higher in saturated fats and lower in polyunsaturated fats.
The study, published in the European Journal of Nutrition in May, highlights the protective effects of a diet higher in polyunsaturated fats.
"If you try to eat fairly healthy most of the time and eat a diet that's higher in these polyunsaturated fats on a regular basis, when you do occasionally splurge or have meals high in saturated fats, it's not quite as detrimental," said Jamie Cooper, the study's senior author and an associate professor in the department of foods and nutrition in the UGA College of Family and Consumer Sciences.
Researchers studied 26 participants, 16 of whom completed a seven-day diet high in polyunsaturated fats—in this case, through whole foods such as walnuts, wild-caught Alaskan keta salmon, tuna, flax seed oil, grapeseed oil and canola oil, along with fish oil supplements—while 10 consumed a control diet higher in saturated fats that consisted largely of frozen meals. Both groups consumed the same three-day lead-in diet.
Both seven-day diets contained identical percentages of carbohydrates, protein and fat and only differed in the types of fat consumed. The high polyunsaturated fat diet derived twice as much energy—or 21 percent—from polyunsaturated fats than the control diet—at 10 percent.
By the end of the seven-day diet, the high polyunsaturated fat diet participants showed significant decreases in total cholesterol and other markers of "bad" cholesterol such as LDL and triglycerides. These participants also were shown to demonstrate greater fat oxidation compared to the control group.
"By consuming a diet higher in polyunsaturated fat on a regular basis, you're basically walking around with this inherent protection from the cardiometabolic effects of poor, high saturated fat meals," said study co-author Chad Paton, an assistant professor in both the college's foods and nutrition department and the College of Agricultural and Environmental Sciences.
Researchers cautioned that simply occasionally eating meals higher in polyunsaturated fats will not protect against overeating and regularly consuming meals high in saturated fats.
"If on your ‘splurge' day or meal you consume 1,000 excess calories, you are going to put on some fat mass from that," Cooper said. "Even though higher daily polyunsaturated fat consumption can help you burn more fat when eating high saturated fat meals, it can't overcome the fat mass gain that will occur with a large caloric surplus from overeating.
"But if you're fairly consistent in matching your energy balance, meaning your calories in are equaling your calories out, then occasionally having that high saturated fat meal shouldn't lead to as much fat storage in your body if you're eating more of these (high polyunsaturated fat) foods regularly."
The study, "A PUFA-rich diet improves fat oxidation following saturated fat-rich meal," is available online at http://link.springer.com/article/10.1007/s00394-016-1226-9.
The study was funded by the California Walnut Commission. Additional researchers are Jada L. Stevenson from Texas Christian University and Mary K. Miller and Hannah E. Skillman from Texas Tech University.
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