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High omega-6, low omega-3 diet induces trans-generational obesity

Posted Aug 16 2010 12:00am - Chronic dietary excess of linoleic acid (omega-6 fatty acid), coupled with a deficiency in alpha-linoleic acid (omega-3 fatty acid), can increase obesity down the generations.  Researchers writing in the Journal of Lipid Research exposed several generations of male and female adult and young mice to a “Western-like” diet of this type, and then assessed the consequences of such a lipid environment in the human diet. This was demonstrated for the first time by Gérard Ailhaud (Université de Nice-Sophia Antipolis) working in collaboration with three CNRS laboratories and one INRA laboratory.

Omega-6 and omega-3 fatty acids are essential polyunsaturated fatty acids. They are indispensable to the human body, which cannot produce them itself and must therefore source them from food. Omega 6 fatty acids are normally found in maize (corn), which is itself consumed in large quantities by commercial farm animals eaten by many humans (half of our lipid intake comes from meat and dairy products). [Note: grass-fed beef has a lower omega-6 profile, with more omega-3s.] As for omega-3 fatty acids, they are mainly present in grass, flax seed (linseed), walnuts, and fatty fish such as salmon, sardine or mackerel (which contain very high levels of omega-3, and in the longer chain forms DHA and EPA).

In the past forty years, there has been a steady rise in obesity over the generations in Western societies. During the same period, the diet in industrialized countries has seen a quantitative increase in the calories ingested (lipids account for 35 to 40 percent of food intake), high levels of  omega 6 fatty acids and low levels of omega-3 fatty acids . Indeed, the amount of omega-6 fatty acids consumed during the past forty years has rocketed (+250 percent) while that of omega-3 fatty acid consumption has fallen by 40 percent, destabilizing the omega 6/omega 3 ratio. While the French Food Safety Agency (AFSSA) recommends an omega-6/omega-3 ratio of 5/1, actual consumption is 15 omega 6 for 1 omega 3. In the USA, this ratio can even reach 40 omega-6 for every 1 omega-3.

To perform their experiments, the researchers exposed four generations of mice to a Western-style diet, characterized by these same omega 6/omega 3 ratios. As a result, they saw a gradual increase in fat mass over several generations. They also observed the onset of metabolic disorders such as insulin resistance, which is the first step in the development of type 2 diabetes and a stimulation of the expression of the inflammatory genes involved in obesity.

(See generational fat-mass comparison photo of mice )

Thus, in a genetically-stable animal population, exposure to a diet similar to that of developed or developing countries was sufficient to cause the emergence of trans-generational obesity, in line with the data collected in humans. The beneficial role of essential polyunsaturated fatty acids such as omega 6 is well-known in the treatment of hypercholesterolemia, and that of omega-3 fatty acids in cerebral function. But when their intake is unbalanced, these fatty acids can enhance the factors inducing obesity and have serious long-term effects on human health.

The abstract of the article is available free online here:

(Adapted from CNRS )

Reference: A Western-like fat diet is sufficient to induce a gradual enhancement in fat mass over generations. Florence Massiera, et al. Journal of Lipid Research, Vol. 51, 2352-2361, August 2010

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