Fasting and weight-loss restrictive diet practices among 2,700 cancer survivors: results from the NutriNet-Santé cohort.

Nutrition is often used by cancer survivors as a lever to take charge of their own health. However, some dietary behaviors are not currently recommended for patients without medical supervision. Our study aimed at evaluating weight-loss restrictive diets and fasting practices among cancer survivors of the NutriNet-Santé cohort, as well as related socio-demographic and lifestyle factors. In October 2016, 2,741 cancer survivors had completed a specific questionnaire about their practices. Fasting and non-fasting patients (respectively dieting and non-dieting) were compared using logistic regression models. Analyses were weighted according to the age, gender, and cancer location distribution of French cancer cases. 13.8% had already practiced weight-loss restrictive diet as their diagnosis. They were more likely to be women, professionally active, overweight/obese, to use dietary supplements and to have breast cancer (all p < 0.05). 6.0% had already fasted, 3.5% as their diagnosis. They were more likely to be younger, with higher educational level, higher incomes, professionally active, to have a healthy weight, and to use dietary supplements (all p < 0.05). Fasting was associated with the opinion that such practice could improve cancer prognosis (p < 0.0001). Patients who received nutritional information from health care professionals were less likely to practice fasting or weight-loss restrictive diet (0.42[0.27-0.66], p < 0.0001 and 0.49[0.38-0.64], p < 0.0001 respectively). Our study provided original results suggesting that weight-loss restrictive diets are widely practiced by cancer survivors. Fasting was less common in our study though non negligible. Sources of nutritional information received as cancer diagnosis seemed to be a key determinant of these practices.