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A recent Harvard study on dietary fat, one of the largest and longest to date, offers more evidence to consider ditching or reducing unhealthy fat in your diet. The study, published online July 5, 2016, by JAMA Internal Medicine, analyzed the eating habits of more than 126,000 people who were followed for as long as 32 years. The study found that eating more saturated and trans fats ("bad" fats) was associated with a higher risk of dying during the study period, while eating more polyunsaturated and monounsaturated fats ("good fats") was associated with a lower risk of dying. The encouraging news: people in the study who replaced just 5% of their calories from saturated fat with "good" polyunsaturated fats were 27% less likely to die. The findings were only observational: they don't prove that dietary fat has an impact on death risk, but they strongly indicate that it does. Saturated fats are found in butter, lard, and red meat. Trans fats, which are being phased out of foods, are found in items such as doughnuts, pizza, and baked goods. You'll find monounsaturated fats in olive and canola oil, avocados, and many nuts and seeds. Polyunsaturated fats are found in corn and sunflower oils and in fatty fish, such as salmon and mackerel.