Glucids are ubiquitous and yet controversial components of our nutrition. This narrative review focuses on the potential harmful effects of sugars on health, particularly as a risk factor for overweight, obesity or diabetes mellitus. Current guidelines recommend a daily limit of intake, and notably a restriction on added sugars. « Keto » diets and intermittent fasting are trending in this era of sugar mistrust. However, the metabolic benefits are not yet clearly established, and the underlying risks should restrain the prescription of these diets to a population of carefully selected patients.