Flickr New evidence from a long-term study suggests that neither high-carb nor low-carb diets are necessarily great for your health. Scientists studied more than 15,000 people in the US and another 400,000-plus around the world, and found that getting about 50-55% of a day's energy from carbohydrates might be ideal. People who ate significantly more or less carbs than that were more likely to die, according to the study. For years, dieters have had to deal with a lot of conflicting advice on how to eat. First, fat was the bad guy.