When older male mice eat fewer calories, they tend to keep healthier muscles and energy-producing parts inside their cells—especially if their diet includes a lot of saturated fat like from lard.

In male mice on a severely reduced diet, the type of fat they eat matters — lard (like bacon fat) seems to keep their muscle cells healthier at a microscopic level better than vegetable or fish oils.

Even when overweight mice eat much less food, their leg muscles don’t shrink — as long as they get enough protein — showing that muscle loss isn’t inevitable during weight loss.

In male mice eating 40% fewer calories, the type of fat they eat matters — mice live longer on more saturated fats like lard than on unsaturated fats like soybean or fish oil.

People who eat fewer calories for many years have more proteins in their muscles that help clean up damaged proteins and cell parts, which might explain why calorie restriction could slow aging.

In mice on a low-calorie diet, eating more fat from lard (like bacon fat) might help them live longer than eating fats from fish or soybean oil.