If you eat less saturated fat (like butter) and more unsaturated fat (like olive oil) while staying on a low-carb diet, your blood fat levels drop by about 11.5% and your body shows less signs of cellular stress.

If you're a man who's keeping your weight steady and eating very few carbs, doubling the amount of butter and fatty meats you eat won't raise the level of saturated fat in your blood — meaning carbs might be the key link between what you eat and what shows up in your blood.

If you swap out butter and fatty meats for oils and nuts, your 'bad' cholesterol goes down, which helps prevent clogged arteries and heart problems.

If you swap out butter and fatty meats for foods like olive oil and avocados instead of swapping them for bread or sugar, your blood fat levels drop more — and that’s especially true if you already have health risks like high cholesterol or insulin resistance.

If you swap out foods like butter and cheese for things like white bread and sugary snacks, it might raise your blood sugar and fat levels after meals, which could make your heart more likely to get sick.

If men eating low-carb food swap out butter and fatty meats for oils like olive or fish oil, their blood gets more of the good fats that fight inflammation, the bad-to-good fat ratio drops a lot, and their cholesterol and triglycerides still improve.