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A wildly unbalanced consumption of omega-6 versus omega-3 fatty acids is contributing to the growing rates of obesity and type 2 diabetes, two researchers are arguing.

In an editorial appearing in the BMJ journal Open Heart, Artemis P. Simopoulos, MD, of the Center for Genetics, Nutrition and Health in Washington, D.C., and James J. DiNicolantonio, PharmD, of Saint Luke's Mid America Heart Institute and associate editor of the journal, said that "pro-inflammatory and thrombogenic" omega-6's have become far too prominent in the Western diet, at the expense of protective omega-3.

"From an evolutionary perspective, we used to consume an omega-6:3 ratio of around 1:1. However, nowadays we consume an omega-6:3 ratio of around 16:1, setting in motion a metabolic storm in our bodies," DiNicolantio told MedPage Today. "The increase in the intake of refined seed oils and the concomitant reduction in the intake of omega-3 fats (both ALA and EPA/DHA) is the most dramatic dietary change that has occurred in the last 100 years. Never before in human history have we ever consumed these seed oils and they may be increasing the risk of chronic disease including obesity."

The authors also argued against the laws of thermodynamics, in terms of caloric intake, as a driver of the obesity epidemic. "The concept of 'a calorie is a calorie' must be abandoned for reasons described in the commentary and in the "Bellagio Report on Healthy Agriculture, Healthy Nutrition, Healthy People," said Simopoulos in an email.

Advances in modern agriculture are one reason why consumption of omega-6 versus omega-3, commonly found in vegetable, corn and seed oils, has pushed omega-3 to the side, the authors suggested. For example, grain-fed animal byproducts are higher in omega-6, whereas grass-fed animal products, such as milk, are richer in omega-3.

The authors suggest the rising rates of obesity and chronic diseases due to inflammation are a result of this increased consumption. "The evidence suggests that when you consume omega-3 fats they provide fat burning signals in the body, whereas omega-6, particularly from vegetable oils, provides fat storing signals," DiNicolantonio said in an interview. "And now that our balance of omega-6:3 is in favor of the omega-6 we are constantly sending our body signals to store more fat but worse than that, the omega-6 also creates inflammatory fat especially when the dietary intake of omega-3 is low."

Omega-6 and omega-3 have a wide range of opposing effects, specifically impacting obesity and type 2 diabetes. Some of these inverse relationships include omega-6 increasing leptin and insulin resistance, waist circumference, oxidation, triglycerides, inflammation, adipose cells, and white adipose tissue. Similarly, a recent NIH Women's Health Initiative study reported that high concentrations of omega-6 in blood was positively assocatied with increased weight gain in young women. Simopoulos explained in an interview how "the low omega-3 intake and high fructose intake of Western diets lead to an increase in appetite, lipogenesis and obesity."

Historically, the ratio has been growing in favor of omega-6. During the Palaeolithic area, the typical diet involved about equal parts omega-6 to omega-3. Now, some of the highest global ratios can be found in urban India, with a ratio of up to 50:1 ratio of omega-6 to omega-3.

Furthermore, the authors explained that a certain genetic predisposition (haplotype D) disproportionately increases omega-6 levels in the blood when linoleic acid, such as vegetable oil, are consumed. With this genetic feature present, there is a significantly greater risk for obesity and type 2 diabetes, as well as other adverse health outcomes when omega-6 is consumed. Prior research suggests that virtually all Africans carry haplotype D; in African-Americans the prevalence is about 50%.

Overall, Simopoulos and DiNicolantonio suggest there are many small changes that healthcare providers can recommend to their patients, particularly if they are genetically identified as high-risk.

"There is little evidence that consuming industrial seed oils are beneficial to health and actually a fair amount of evidence suggesting harm," DiNicolantonio explained. "Dietary guidelines should not be recommending the consumption of industrial seed oils until further evidence is available. Furthermore, there should be a greater emphasis on increasing the intake of nuts, seeds, and oceanic seafood to increase the intake of both ALA and EPA/DHA. This may not only decrease the risk of numerous chronic diseases but may also help our waistline."

Simopoulos told MedPage Today that a wide-ranging shift in public policy is needed. She urged that official guidelines should stop recommending low-fat diets and that omega-6 and omega-3 fats should be measured and listed separately on food labels. Moreover, she said the U.S. Department of Agriculture, as an agent of food producers, should not be involved in developing dietary recommendations. Instead, the government should establish a separate nutrition agency.