Very difficult, Sadly nutrition research is not yet very conclusive on what is good and what is bad for our health. (It's very difficult to have correct experim

Very difficult, Sadly nutrition research is not yet very conclusive on what is good and what is bad for our health. (It's very difficult to have correct experiments as the volunteers never have the same physiology) And our nutriments needs may be very specific to one's genetics and activity level. Sugar is fuel for the brain and the body, it is not necessary bad, but abusing it is bad. Maybe sugar (eg pasta) is bad when mixed with other ingredients and healthy with others. It is extremely difficult to reach a good consensus even if you read the litterature. And usually (micro)nutriments have trade-offs : good for somethings bad for others. Look at the different kind of diet, they are all based on different researches and can be extremely different while all are using 'valid' research data. The main idea behind them is usually to have 'good' proportions between macronutrients (each diet define a different proportion) while keeping the number of kcal in the range you want to reach your objectives. For a first rule of thumb that I would use: abusing in any direction is bad. Sugar is ok in 'small' quantities, fat, etc also. However reality is way more messy :)