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.