Objective: To examine the relationship between the strictness of long-term raw food diets and body weight loss, underweight and amenorrhea. Methods: In a cross-sectional study 216 men and 297 women consuming long-term raw food diets (3.7 years; SE 0.25) of different intensities completed a specially developed questionnaire. Participants were divided into 5 groups according to the amount of raw food in their diet (70–79, 80–89, 90–94, 95–99 and 100%). A multiple linear regression model (n = 513) was used to evaluate the relationship between body weight and the amount of raw food consumed. Odds of underweight were determined by a multinomial logit model. Results: From the beginning of the dietary regimen an average weight loss of 9.9 kg (SE 0.4) for men and 12 kg (SE 0.6) for women was observed. Body mass index (BMI) was below the normal weight range (< 18.5 kg/m2) in 14.7% of male and 25.0% of female subjects and was negatively related to the amount of raw food consumed and the duration of the raw food diet. About 30% of the women under 45 years of age had partial to complete amenorrhea; subjects eating high amounts of raw food (> 90%) were affected more frequently than moderate raw food dieters. Conclusions: The consumption of a raw food diet is associated with a high loss of body weight. Since many raw food dieters exhibited underweight and amenorrhea, a very strict raw food diet cannot be recommended on a long-term basis.