Here is a study claiming a noticeable impact on mortality rates from eating red meat. Weight is considered to some degree via body mass index, but I have to wonder if this only reflects a modest association of red meat consumption with other, less healthy lifestyle choices rather than an actual red-meat-based mechanism - as an obvious candidate mechanism for that isn't also present in all meat consumption isn't springing to mind: researchers "found that red meat consumption is associated with an increased risk of total, cardiovascular, and cancer mortality. The results also showed that substituting other healthy protein sources, such as fish, poultry, nuts, and legumes, was associated with a lower risk of mortality. ... [Researchers] observed 37,698 men from the Health Professionals Follow-up Study for up to 22 years and 83,644 women in the Nurses' Health Study for up to 28 years who were free of cardiovascular disease (CVD) and cancer at baseline. Diets were assessed through questionnaires every four years. ... One daily serving of unprocessed red meat (about the size of a deck of cards) was associated with a 13% increased risk of mortality, and one daily serving of processed red meat (one hot dog or two slices of bacon) was associated with a 20% increased risk. ... These analyses took into account chronic disease risk factors such as age, body mass index, physical activity, family history of heart disease, or major cancers. ... Replacing one serving of total red meat with one serving of a healthy protein source was associated with a lower mortality risk: 7% for fish, 14% for poultry, 19% for nuts, 10% for legumes, 10% for low-fat dairy products, and 14% for whole grains. The researchers estimated that 9.3% of deaths in men and 7.6% in women could have been prevented at the end of the follow-up if all the participants had consumed less than 0.5 servings per day of red meat."