Winter 2017

Replace Your Fats

There are benefits to trading bad fats and carbs for good fats.

Here’s a diet swap with lots of evidence behind it: Eating more unsaturated fats, especially polyunsaturated fats, in place of carbs or saturated fats lowers blood sugar levels and improves insulin resistance, according to a meta-analysis of data from 102 studies.

The study, led by Dariush Mozaffarian, dean of the Friedman School, and Fumiaki Imamura, N09, a senior investigator scientist at the University of Cambridge, provides new evidence for the effects of dietary fats and carbohydrates on the regulation of glucose and insulin levels and several other metrics linked to type 2 diabetes. The results were published in PLOS Medicine.

The team identified and summarized findings from randomized controlled feeding trials that involved 4,660 adults; the meals they ate varied in the types and amounts of fat and carbohydrates. The researchers then evaluated how the variations in diet affected measures of metabolic health, including blood sugar, blood insulin, insulin resistance and sensitivity, and the ability to produce insulin in response to blood sugar.

Rates of insulin resistance and type 2 diabetes are rising sharply worldwide, highlighting the need for new, evidence-based preventive strategies. While a healthy diet is clearly a cornerstone of such efforts, the effects of different dietary fats and carbohydrates on metabolic health have been controversial, leading to confusion about specific dietary guidelines and priorities.

“The world faces an epidemic of insulin resistance and diabetes,” said Mozaffarian, the senior author on the study. “Our findings support preventing and treating these diseases by eating more fat-rich foods like walnuts, sunflower seeds, soybeans, flaxseed, fish and other vegetable oils and spreads in place of refined grains, starches, sugars and animal fats.”

“This is a positive message for the public,” he added. “Don’t fear healthy fats.”

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