This study aimed to investigate 1) the longitudinal associations between food patterns and body weight in young adulthood, and 2) how food patterns of young adults relate to food consumption in early, middle and late childhood. The study sample includes 700 participants of the Québec Longitudinal Study of Child Development. During childhood, frequency of consumption of various foods was reported on ten occasions between 1.5 and 13 years. At age 22 years, food frequency questions (with quantities) were used to derive four food patterns (labeled healthy, beverage-rich, protein-rich, and high-energy-density) through exploratory factor analysis. Self-reported height and weight were collected at 22 and 23 years. Regression analyses were performed to assess associations between 1) food patterns and weight outcomes a year later (BMI, BMI change, and overweight status); 2) frequency of consumption of eight food groups in childhood and food patterns in adulthood. Dietary habits characterised by the consumption of vegetables, fruit, plant-based sources of protein and whole-grain cereal products were related to a lower risk of obesity a year later. Conversely, dietary habits characterised by a high consumption of energy-dense foods, of animal sources of proteins and, among women, of high quantities of liquids were associated with higher risk of excess weight a year later. Healthier food choices in childhood were associated with healthier food patterns in young adulthood. These findings reinforce the value of preventive dietary interventions in the early years to foster eating environments that favour healthy eating and healthy weights in adulthood.