Conversely, a non-linear dose–response relationship was observed between dietary fiber intake and serum Klotho levels in the overweight and obese groups, as well as male and female groups (overweight and obesity: p for non-linearity = 0.005, male: p for non-linearity = 0.024, female: p for non-linearity = 0.014). Here, KL is linked to obesity due to melanocortin 4 receptor deficiency.