Introduction Competing in aesthetic sports increases the risk of low energy availability and associated health impairments. Fitness physique sport is a popular, but understudied aesthetic sport. We evaluated health and symptoms of relative energy deficiency in sport (RED-s) in female fitness athletes (FA) and female references (FR) during a competitive season. Methods Totally, 25 FA and 26 FR, mean (SD) age of 28.9 (5.7), were included. Assessments were at baseline (T1), 2-weeks pre-competition (T2), and 1-month post-competition (T3), by dual-energy x-ray absorptiometry scan, indirect calorimetry, diet registration, The Low Energy Availability in Females Questionnaire, The Beck Depression Inventory, and Eating Disorder Examination Questionnaire (EDE-Q). Results A history of eating disorders was reported by 35% FA and 12% FR. There were no between-group differences at T1, besides less mean (99% CI) fat mass (FM) of 3.1 kg (-0.4, 6.5) in FA (P = .02). At T2, FA had lower BW of 6.7 kg (-12.0, -1.3), fat mass of -9.0 kg (-12.5, -5.5), and resting heart rate of -8.0 beats per minute (-14.5, -1.5) compared to FR (P <= .006). FA reduced resting metabolic rate by -191 kcal (-11, -371) and increased symptoms of gastrointestinal dysfunction (GD) by 1.4 points (0.3, 2.5) and prevalence of amenorrhea from 8% to 24%, (P < .003). At T3, there was a between-group difference in fat mass, and a high number of FA with amenorrhea and GD. Conclusion Manifestation of symptoms of RED-s, some with persistence one-month post-competition, raises concern for the health of FA and those complying with the fit body ideal.