The Effects of Intensive Weight Reduction on Body Composition and Serum Hormones in Female Fitness Competitors

Abstract

Worries about the potential negative consequences of popular fat loss regimens for aesthetic purposes in normal weight females have been surfacing in the media. However, longitudinal studies investigating these kinds of diets are lacking. The purpose of the present study was to investigate the effects of a 4-month fat-loss diet in normal weight females competing in fitness-sport. In total 50 participants finished the study with 27 females (27.2 ± 4.1 years) dieting for a competition and 23 (27.7 ± 3.7 years) acting as weight-stable controls. The energy deficit of the diet group was achieved by reducing carbohydrate intake and increasing aerobic exercise while maintaining a high level of protein intake and resistance training in addition to moderate fat intake. The diet led to a ~12% decrease in body weight (P < 0.001) and a ~35–50% decrease in fat mass (DXA, bioimpedance, skinfolds, P < 0.001) whereas the control group maintained their body and fat mass (diet × group interaction P < 0.001). A small decrease in lean mass (bioimpedance and skinfolds) and in vastus lateralis muscle cross-sectional area (ultrasound) were observed in diet (P < 0.05), whereas other results were unaltered (DXA: lean mass, ultrasound: triceps brachii thickness). The hormonal system was altered during the diet with decreased serum concentrations of leptin, triiodothyronine (T3), testosterone (P < 0.001), and estradiol (P < 0.01) coinciding with an increased incidence of menstrual irregularities (P < 0.05). Body weight and all hormones except T3 and testosterone returned to baseline during a 3–4 month recovery period including increased energy intake and decreased levels aerobic exercise. This study shows for the first time that most of the hormonal changes after a 35–50% decrease in body fat in previously normal-weight females can recover within 3–4 months of increased energy intake.

Physical health and symptoms of relative energy deficiency in female fitness athletes

“…Changes in body composition during the study period (T1-T3) are illustrated in Figure 4. In FA, mean (99% CI) %BF were 25% (22,28) at T1, 17% (14,20) at T2, and 21% (18,24) at T3, with significant differences at T2 and T3 compared to T1 (P < .001). The corresponding findings for FR were 29% (26, 31), 30% (27,32), and 29% T A B L E 1 Demographic presentation of fitness athletes (FA) and female references (FR) at baseline (T1).…”

“…Amenorrhea is previously reported in FA, with long-term persistence despite normalization of BW and composition. 14,15,17,20 Present guidelines suggest BF% of 12% to be the lowest recommended level in females to avoid negative health effects. 6 In the current study, the FA reached their lowest mean BF% of 17% at T2, while case studies of FA have reported levels of 9%-11% [14][15][16][17] and cohort studies means of 13%-18%.…”

“…3,4 Hence, there are reasons for concern for the health of these athletes. At the time, only four case studies [14][15][16][17] and four cohort publications [18][19][20][21] report on health outcomes in females related to dieting for fitness sport participation. Among the publications with post-competition measures, 14,17,20,21 changes in BW and composition were reported to be temporary, with return to or above baseline 14,17,20 or normal, healthy levels 21 within 1-4 months post-dieting.…”

“…At the time, only four case studies [14][15][16][17] and four cohort publications [18][19][20][21] report on health outcomes in females related to dieting for fitness sport participation. Among the publications with post-competition measures, 14,17,20,21 changes in BW and composition were reported to be temporary, with return to or above baseline 14,17,20 or normal, healthy levels 21 within 1-4 months post-dieting. Unfortunately, shortages in these studies are either lack of reports on BMD, 14,16,17,21 lack of psychometric outcomes, 14,15,21 lack of post-competition measures, 15,16 or lack of comparisons to a healthy reference group not participating in this sport.…”

“…Unfortunately, shortages in these studies are either lack of reports on BMD, 14,16,17,21 lack of psychometric outcomes, 14,15,21 lack of post-competition measures, 15,16 or lack of comparisons to a healthy reference group not participating in this sport. [14][15][16][17]20,21 Furthermore, site-specific BMD, such as spine BMD and proximal femur BMD, is more prone to the negative effect from low BW or dieting, while total BMD is less likely to reflect early changes. 24 Only one of the previous studies reported on site-specific BMD, concluding with no negative effect, despite reporting a seemingly overall low BMD.…”