The findings showed that all three dietary plans promoted similar weight loss. Insulin-sensitive women lost the most weight with a low-fat diet but that strategy did not result in the most benefit for lipid levels.
The walnut-rich diet had the most impact on cholesterol levels by decreasing low-density lipoprotein (LDL), or bad cholesterol, and increasing beneficial high-density lipoprotein (HDL). The high-fat, low-carb group, which consumed monounsaturated fats, did not experience the same beneficial effects as the walnut-rich diet, which featured polyunsaturated fatty acids.
At six months, the average weight loss was almost 8 percent among all groups.
"This weight loss may not put these women at their ideal weight, but it made a significant reduction in their risk of cardiovascular and other diseases," said Rock. "This level of weight loss is achievable and can have a dramatic impact on their quality of life."
Insulin sensitivity was assessed in the study because people who are overweight usually have some degree of insulin resistance. Higher amounts of insulin are more likely to cause cells to lose their ability to regulate growth, a precursor to cancer.
"Diet composition impacts lipid levels, but the critical factor to lose weight continues to be to burn more calories than you consume," said Rock.