Omega-3, western diet and overweight


First of all, let’s clarify what is considered overweight y obesity from the perspective of health. Only weight that is higher than what is considered as a healthy weight for a given height is defined as overweight or obesity. And the tool used to assess weight in relation to height is the Body Mass Index (BMI): With the metric system, the formula for BMI is weight in kilograms divided by the square of height in meters (formula: weight (kg) / [height (m)]2). If you want to use pounds and inches, calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703 (formula: weight (lb) / [height (in)]2 x 703).

For adults (men and women) 20 years old and older, BMI is interpreted as follows:

  • If BMI is less than 18.5, underweight.
  • If BMI is 18.5 to 24.9, normal or healthy weight.
  • If BMI is 25.0 to 29.9, overweight.
  • If BMI is 30.0 or higher, obese.

Since the Industrial Revolution, western diets contain excessive levels of omega-6 fatty acids but very low levels of omega-3 fatty acids. The intake of omega-6 has increased and the intake of omega-3 has decreased, resulting in a large increase in the omega-6/omega-3 ratio from 1:1 during human evolution to approximately 20:1 today. This change is related with the increase of overweight and obesity in western societies: A high omega-6 fatty acids intake and a high omega-6/omega-3 ratio are associated with weight gain, whereas a high omega-3 fatty acids intake decreases the risk for weight gain. And it has been shown that obesity can be reversed with increased intake of EPA and DHA (the main omega-3 fatty acids).

A balanced omega-6/omega-3 ratio is important for health and in the prevention and management of obesity.