Let’s face it…the “eating fat will make you fat” hypothesis just doesn’t hold water. Dietary fat been vilified since the Ancel Keys days and his Seven Country Study in the late 50’s where he tried to prove the correlation between heart disease and eating fat saturated fat. Interestingly, Key’s study did find a correlation between eating saturated and fat and heart disease, but his experiments used saturated fats made from artificially processed vegetable oils using a process called hydrogenation. Hydrogenated vegetable oils contain not just saturated fat but also trans fat and a whole host of other unnatural molecules. Trans fat does indeed raise blood cholesterol, as well as lead to heart attacks and strokes.
Let’s get to the meat of why eating fat doesn’t make you fat. Of the three macronutrients, protein, carbohydrates, and fat, dietary fat is least likely to stimulate an insulin response. Remember, insulin is the queen hormone of weight loss/gain. In a non-diabetic person insulin is produced in the pancreas and allows the body to use glucose (from carbs) for energy for future use. When insulin is elevated it tells the body to store sugar for later and any excess is stored at fat.
So, how does eating fat make you fat? While fat is higher in calories, fat is very satiating, therefore you don’t require as much food and you won’t be hungry within 30 mins. If you consumed a donut for breakfast the insulin is released in response to the high sugar surge. The body says I better hang on to this energy for later and store it just in case.
The “eating fat makes you fat” hypothesis makes sense if you eat nothing but bacon all day every day, but I would imagine your satiety hormones would kick in to stop you from over doing it.
I’ve done my own experimentation with trying to overeat fat and I failed. One morning I cooked up 4 strips of bacon, 3 eggs fried in the bacon fat, an avocado and a piece of low carb toast with butter. I couldn’t get past eating 2 pieces of bacon and 1 egg when the feeling of fullness set in. Did I just poke a hole in another theory that eating fat will make you fat?