The National Nutrition and Health Program (PNNS) has clearly demonstrated its commitment to implementing a nutritional prevention policy targeting disadvantaged populations since its inception in 2001, given the strong link identified between diet, socioeconomic status, and health. Low socioeconomic status is generally associated with dietary imbalances, a higher prevalence of chronic diseases, and reduced life expectancy. Obesity, as well as underweight conditions, are more common among populations with low socioeconomic status or living in precarious circumstances, with a gap that is gradually widening between the two extremes of the social scale, particularly among adolescents. Several hypotheses have been put forward to explain the socioeconomic gradient of obesity and chronic diseases, notably the physical and economic barriers preventing the most disadvantaged from accessing a balanced diet. Budget constraints effectively steer dietary "choices" toward foods with low nutritional density (content of protective nutrients per 100 kilocalories) and high energy density (calorie content per 100 grams). (R.A.)