The imbalance between omega-3 and omega-6 in the diet, not solely energy intake and expenditure, is suggested to play a significant role in obesity.
Nutrition policies that have centered on the mismatch between "calories in and energy out" in the belief that all calories are equal, have "failed miserably over the past 30 years," disputes Dr. Artemis Simopoulos, of the Center for Genetics, Nutrition, and Health in Washington, D.C., and Dr. James DiNicolantonio, of Saint Luke's Mid America Heart Institute in Kansas.
Drs. Simopoulos and DiNicolantonio note - in an editorial published in the online journal Open Heart - that humans evolved on a diet that had equal amounts of omega-6 and omega-3 fatty acids. This intrinsic balance is critical to babies' development during pregnancy and breast-feeding, and in preventing and managing chronic diseases.
Now, this 1:1 ratio has been replaced by an omega-6 to omega-3 ratio of 16:1. This substantial ratio difference has emerged as a consequence of significant changes in the food supply over the last 100 years.
Food technology and modern agriculture have led to production of vegetable oils - such as sunflower, safflower, cottonseed, soybean, and corn - rich in omega-6 fatty acids, and a swap in animal feeds from grass to grain. Traditionally, animals grazed on grass containing omega-3, whereas the grains, corn, and soy that they are now fed are high in omega-6.
The change in oils and animal feed has increased levels of linoleic acid and arachidonic acid - two types of omega-6. Linoleic acid levels have soared in the diet from oils and arachidonic acid from meat, eggs, and dairy.
High dietary intake of omega-6 has several adverse outcomes, according to researchers. The high levels of omega-6 can lead to increased white fatty tissue and chronic inflammation, which are both hallmarks of obesity and linked to type 2 diabetes, heart disease, metabolic syndrome, and cancer.
Omega-6 can also prevent the browning of white fatty tissue to "good" energy-burning brown fatty tissue and can increase the risk of blood clotting.
Substituting meat for fish, changing cooking oils may rebalance fats
While the body needs both omega-3 and omega-6, the balance between the two is crucial, say the researchers. Fatty acids act directly on the nervous system, influencing food intake and sensitivity of the hormones involved in blood sugar control and appetite suppression.
Omega-3 and omega-6 are metabolically and functionally different. Previous studies have linked omega-3 fatty acids to a decrease in the development of fatty tissue and weight loss, while high concentrations of omega-6 have been associated with an increased risk of weight gain
The authors point out that different populations metabolize fatty acids differently, which makes them more or less at risk of the consequence of an imbalance. The authors write:
"The time has come to return the omega-3 fatty acids in the food supply and decrease the omega-6 fatty acids by changing the cooking oils and eating less meat and more fish. The composition of the food supply must also change to be consistent with the evolutionary aspects of diet and the genetics of the population."
"The scientific evidence to balance the omega-6 to omega-3 ratio is robust and necessary for normal growth and development, prevention and treatment of obesity and its comorbidities including diabetes, cardiovascular disease, and cancer," they add.
Drs. Simopoulos and DiNicolantonio say that these objectives can be accomplished by studies focusing on the metabolism of nutrients, genes, and their function.
"It is the responsibility of the governments and international organizations to establish nutrition policies based on science and not continue along the same path of focusing exclusively on calories and energy expenditure, which have failed miserably over the past 30 years," they conclude.