Dr. Michael Eades of Protein Power fame thinks he knows why we’ve gotten fat starting 35 years ago:
Along with carbohydrates, vegetable oils have increased dramatically in the typical American diet. Over the same time period, we’ve all started eating away from home more and more, so that we’ve lost control of exactly what kinds of fats we’ve been eating.
Click the link for the details of his hypothesis, which involves the effects of various dietary fats and carbohydrates on intracellular energy metabolism and insulin resistance.
PS: Even if you think proteins are powerless, my books are made without vegetable oils.