The researchers agreed that no specific fat to carbohydrate ratio is best for everyone, and that an overall high-quality diet that is low in sugar and refined grains will help most people maintain a healthy weight and low chronic disease risk.
"This is a model for how we can transcend the diet wars," said lead author David Ludwig, professor in the Department of Nutrition at Harvard Chan School and a physician at Boston Children's Hospital. "Our goal was to assemble a team with different areas of expertise and contrasting views, and to identify areas of agreement without glossing over differences."
The review was published online November 15, 2018 in Science.
The authors laid out the evidence for three contrasting positions on dietary guidelines for fat and carbohydrate consumption:
- High consumption of fat causes obesity, diabetes, heart disease, and possibly cancer, therefore low-fat diets are optimal.
- Processed carbohydrates have negative effects on metabolism; lower-carbohydrate or ketogenic (very low-carbohydrate) diets with high fat content are better for health.
- The relative quantity of dietary fat and carbohydrate has little health significance--what's important is the type of fat or carbohydrate source consumed.
Within their areas of disagreement, the authors identified a list of questions that they said can form the basis of a new nutrition research agenda, including:
- Do diets with various carbohydrate-to-fat ratios affect body composition (ratio of fat to lean tissue) regardless of caloric intake?
- Do ketogenic diets provide metabolic benefits beyond those of moderate carbohydrate restriction, and especially for diabetes?
- What are the optimal amounts of specific types of fat (including saturated fat) in a very-low-carbohydrate diet?