A nutritionist theorizes that eating fat-free foods is unhealthy and may cause weight gain. Her studies suggest that dieters must eat twice as many fat-free foods to feel satisfied, while others allow themselves to eat abundant amounts of fat-free foods regardless of calorie content. Focusing on the fruit-and-vegetable-rich Mediterranean diet, she advises readers to consume moderate amounts of heart-healthy unsaturated fatty acids found in fish oil, olive oil, walnuts, and avocados. In addition to promoting hormone and nerve cell growth, polyunsaturates and omega-3 fatty acids may prevent certain cancers and reduce the risk of heart attack.