The nutrition component of the Study on Health, the Environment, Biomonitoring, Physical Activity, and Nutrition (Esteban 2014–2016) aimed to describe dietary intake, physical activity, sedentary behavior, and the nutritional status of the population residing in metropolitan France. This nutrition component was a follow-up to the National Nutrition and Health Survey (ENNS), conducted in 2006–2007, to obtain reliable data on changes in indicators that had already been collected 10 years earlier. Esteban was conducted on a sample of children aged 6 to 17 and adults aged 18 to 74 residing in metropolitan France. Following a random selection based on a three-stage sampling plan, subject enrollment took place from April 2014 to March 2016 to account for seasonal variations in diet and potential exposures. Data collection on physical activity and sedentary behavior aimed to assess the population’s level of physical activity and its alignment with health recommendations. The goal was to measure the level of physical activity (in terms of frequency, duration, and intensity) and the level of sedentary behavior (daily duration of sedentary activities, time spent in front of a screen) among adults and children, across all their activities (work, school, household, leisure, etc.). These data were collected via self-administered questionnaires and covered a representative national sample of 2,682 adults and 1,182 children aged 6 to 17. The results indicate that in 2015, 53% of women and 71% of men met the WHO recommendations for physical activity. There was no difference based on educational attainment. Between 2006 and 2015, physical activity levels decreased among women regardless of age. They increased among men aged 40–54 and remained stable in other age groups. Nearly 90% of adults (regardless of gender or educational level) reported 3 hours or more of sedentary activity per day, and 42% reported more than 7 hours. One in five adults had both risk factors: a high level of sedentary behavior and a low level of physical activity, below the recommendations. The average daily time spent in front of a screen has risen sharply over the past 10 years. While in 2006, 53% of adults reported spending 3 hours or more in front of a screen each day outside of work, this figure rose to 80% in 2015. This increase affected all age groups and educational levels, but was more pronounced among women. Finally, although sedentary behavior is widespread among the adult population as a whole, it appeared to be more attributable to “sedentary leisure activities” (such as time spent in front of a screen) among those with lower levels of education, and more attributable to sedentary work among those with higher levels of education. Regarding children aged 6–17, only 51% of boys and 33% of girls met the WHO’s physical activity recommendations in 2015. Physical activity levels varied by gender and age. Children aged 6–10 were the most active. Seven out of 10 boys and one in two girls met the recommendations in this age group, compared to one-third of boys and one-fifth of girls over the age of 10. Physical inactivity increased significantly after age 11, with a more pronounced increase among girls. There has been no significant change in children’s physical activity levels over the past 10 years. However, between 2006 and 2015, a trend toward increased physical activity among 15- to 17-year-olds was observed. Regarding sedentary behavior, nearly half of children aged 6–10 reported spending 3 hours or more in front of a screen each day; this proportion reached 70% among 11–14-year-olds, 71% of girls, and 87% of boys aged 15–17. On average, between 2006 and 2015, daily screen time increased by 25 minutes among children aged 6–10, by 1 hour and 15 minutes among children aged 11–14, and by nearly 2 hours among those aged 15–17. These results highlight persistently low levels of physical activity and high levels of sedentary behavior among adults and children residing in mainland France in 2015, as well as a near-universal decline in these indicators over the past 10 years. It therefore appears necessary, from a public health perspective, to take joint action to increase the population’s level of physical activity and limit the time spent in sedentary behaviors. Particular attention must be paid to women, among whom these factors have deteriorated more markedly over the past 10 years.