Olfaction is crucial for many aspects of daily life and its alteration is quite common. Here, we set up a large-scale investigation of olfactory deficits in a sample of French individuals in order to examine the prevalence of smell dysfunction and its effects on eating behavior across lifespan, by combining self-reports and psychophysical testing. In a sample of 3685 male and female individuals aged 4 to 89 years old, we showed that the overall prevalence of olfactory dysfunction as measured by psychophysical testing was 17% and varied with age and gender: from 10% in 4-12 year-old children to >30% after 60 years of age; overall, women were less often affected than men. When olfactory abilities were self-evaluated, the prevalence was 6%, suggesting that a large majority of participants were unaware of their olfactory disorder. The prevalence of qualitative smell disorders (parosmia and phantosmia) was much lower (1%). In terms of eating behavior, the effects were present but small: olfactory deficits impact eating behavior of people in different age groups differently. Taken together, these findings highlight the high prevalence of olfactory dysfunctions in the general population, not only in the elderly. They also emphasize the potential consequences of smell dysfunctions on eating behavior. The present results should attract health services' attention since smell dysfunctions may have consequences on nutrition and health especially in the elderly.