Participant characteristics
Forty seven natural bodybuilders (33 male) were recruited. The male cohort included 8 PROs and 25 AMAs. All male PROs had placed in the top five of DFAC or WNBF PRO World Finals. The cohort also included 3 competitors who had won their weight class at the aforementioned World Finals, and a two-time overall PRO World champion. The female cohort included 14 competitors: 5 PROs (4 figure, 1 bodybuilding), and 9 AMAs (5 figure, 2 masters figure, 1 bodybuilding, 1 athletic). Amongst the PRO females, 3 previously placed in the top 3 at the DFAC PRO World Finals. Complete dietary information was available for all participants. Participant characteristics including diet length are presented in Table 1.
Table 1 Self-reported Characteristics of British Professional and Amateur Natural Bodybuilders Preparing for Competition Nutrient intake
Energy and macronutrients intake
Total macronutrient and energy intake for the start, middle and end of contest preparation are reported in Table 2. Results of the repeated measures ANOVA identified a significant reduction in energy and macronutrients as preparation progressed (p time < 0.05) in both males and females. Total CHO and energy intake was significantly higher (p division < 0.05) in PRO men compared to AMAs. Furthermore, there was a trend for a higher fibre intake in PRO men compared to AMAs (p division = 0.068) as well as an interaction over time (p time x division = 0.079). Cohen’s d effect size analysis indicated a large effect size for a higher total CHO (start: d = 1.1 CI [0.3, 2.0], middle: d = 1.1 CI [0.3, 2.0], end: d = 1.4 CI [0.5, 2.4]) and energy intake (start: d = 1.1 CI [0.3, 2.0], middle: d = 0.9 CI [0.1, 1.8], end: d = 1.4 CI [0.6, 2.3]) in PRO men compared to AMAs. No other significant effect sizes were detected between PRO and AMA men: protein start d = 0.5 CI [0.0, 1.3], middle d = 0.4 CI [− 0.4, 1.2], end d = 0.5 CI [− 0.3, 1.3]; fat start d = − 0.2 CI [− 1.0, 0.6], middle d = − 0.5 CI [− 1.3, 0.3], end d = 0.1 CI [− 0.9, 0.7]; fibre start d = 0.8 CI [0.0, 1.7], middle d = 0.5 CI [− 0.3, 1.3], end d = 0.8 CI [0.0, 1.7]. Among females no significant effect sizes were detected between PROs and AMAs: protein start d = 0.0 CI [− 1.1, 1.1], middle d = 0.1 CI [− 1.0, 1.2], end d = 0.1 CI [− 1.0, 1.2]; CHO start d = 1.1 CI [− 0.4, 1.9], middle d = 0.2 CI [− 0.4, 1.9], end d = 0.5 CI [− 0.6, 1.6]; fat start d = 0.2 CI [− 1.3, 0.9], middle d = 0.5 CI [− 0.6, 1.7], end d = 0.0 CI [− 1.1, 1.1]; fibre start d = 0.3 CI [− 0.8, 1.5], middle d = 0.1 CI [− 1.7, 1.1], end d = 0.3 CI [− 0.8. 1.4]; energy start d = 0.4 CI [− 0.7, 1.5], middle d = 1.0 CI [− 0.2, 2.2], end d = 0.4 CI [− 0.7, 1.6]. As a percentage of energy intake, macronutrient intake among males was: CHO PRO 49.2 to 49.7%, AMA 39.8 to 43.4%; protein PRO 31.2 to 34.0%, AMA 34.0 to 39.3%; fat PRO 13.2 to 15.3%, AMA 17.7 to 19.7%. Macronutrients as a percentage of energy among females was: CHO PRO 36.8 to 44.1%, AMA 31.5 to 39.0%; protein PRO 34.6 to 43.0%, AMA 36.7 to 45.5%; fat PRO 17.8 to 22.5%, AMA 20.8 to 21.1%.
Table 2 Total Macronutrient and Energy of British Professional and Amateur Natural Bodybuilders Mean macronutrient and energy intake scaled for body mass is reported in Table 3. Repeated measures ANOVA identified a number of significant differences and trends for a reduction in fat (p time = 0.024), protein (p time = 0.060) and energy (p time = 0.089) during preparation among males. Male PROs also consumed significantly (p division = 0.034) more CHO than AMAs although not consistently over time (p time x division = 0.135). Effect size analysis indicated a large effect for greater CHO intake scaled to body mass among male PROs compared to AMAs (start d = 0.7 CI [− 0.2, 1.5], end d = 1.0 CI [0.2, 1.8]). No other significant effect sizes were detected between the male divisions: protein start d = 0.1 CI [− 0.7, 0.9], end d = 0.1 CI [− 0.7, 0.9]; fat start d = − 0.5 CI [− 1.3, 0.3], end d = − 0.2 CI [− 1.0, 0.6]; energy start d = 0.4 CI [− 0.4, 1.2], end d = − 0.8 CI [0.0, 1.6]. No significant effect sizes were detected between female PROs and AMAs: protein start d = 0.0 CI [− 1.1, 1.1], end d = 0.0 CI [− 1.1, 1.1]; CHO start d = 0.8 CI [− 0.3, 1.9], end d = 0.4 CI [− 0.7, 1.5]; fat start d = 0.1 CI [− 1.0, 1.2], end d = 0.1 CI [− 1.2, 1.0]; energy start d = 0.6 CI [− 0.5, 1.8], end d = 0.3 CI [− 0.8, 1.4].
Table 3 Macronutrient and Energy Intake Scaled for Body Size of British Professional and Amateur Natural Bodybuilders Diet diversity
Male PROs and AMAs reported 14.9 ± 4.9 and 15.8 ± 4.6 food items, while female PROs and AMAs reported 13.5 ± 4.4 and 16.7 ± 4.7 food items respectively, throughout preparation. There was no significant difference (Males: t (97) = 1.039, p = 0.303, females: t (40) = 1.044, p = 0.301) in the number of food items consumed throughout preparation between PROs and AMAs of either sex. The contribution different food groups make to PRO and AMA competitors’ diets is presented in Fig. 1a–d. Male PROs consumed more red meat (z = 2.326, p = 0.020), fruit (z = 2.206, p = 0.027), and sugar and confectionary items (z = 4.357, p < 0.001) than AMA. In contrast, male AMA consumed more, cereals (z = 2.398, p = 0.016), and eggs (z = 3.358, p = 0.001), than PROs. In the female cohort, AMAs consumed significantly more (z = 3.073, p = 0.002) poultry than PROs, while PROs consumed significantly more (z = 2.128, p = 0.033) food from marine sources than AMAs. No other significant differences (p > 0.05) were detected between sexes. Cereals, dairy, white meat and vegetables were the most popular food items consumed. Cereals were consumed mainly as oats and white or brown rice; dairy was consumed mainly as protein powder and yoghurt; white meat as poultry; and vegetables as broccoli, spinach and mushrooms. Other popular groups included tubers as white and sweet potatoes, fruit as raspberries and blueberries. No competitors reported consuming alcohol, sugar sweetened beverages, composite diet dishes, animal fats for cooking or food imitates e.g. Quorn.
Estimated energy requirements and energy deficit
There was no significant difference (p > 0.05) between PRO and AMA, of either sex for estimated BMRs with and without the addition of PAL (Additional file 2). The EED was significantly greater in male AMA compared to PROs at the start (t (30) 2.57, p = 0.034, d = 1.0, CI [0.2, 1.9], PRO: 2.0 ± 5.5 kcal/kg BW, AMA: − 3.39 ± 5.2 kcal/kg BW) and end of preparation (t(31) 3.32, p = 0.002, d = 1.3, CI [0.5, 2.2], PRO: − 1.1 ± 6.0 kcal/kg BW, AMA: − 9.3 ± 6.1 kcal/kg BW). There were no significant differences or effect sizes detected for EED in the female cohort at either the start (t(12) 0.60, p = 0.558, d = 0.3 CI [− 0.7, 1.4], PRO: 1.8 ± 8.5 kcal/kg BW, AMA: − 0.8 ± 7.1 kcal/kg BW), or end (t(12) 0.49, p = 0.634, d = 0.3 CI [− 0.8, 1.4], PRO: − 7.3 ± 4.5 kcal/kg BW, AMA: − 10.0 ± 7.5 kcal/kg BW) of preparation.
Dietary supplements
The number of supplements reported by male and female competitors was 6.7 ± 2.7, and 8.8 ± 1.8, respectively. There was a trend (t (31) = 1.71, p = 0.097) for male PROs to use more supplements (PRO: 8.1 ± 2.8, AMA: 6.3 ± 2.6). Dietary supplements reported by competitors are presented in Table 4. Moreover, female PRO consumed significantly more (t (12) = 2.54, p = 0.026) supplements than AMAs (PRO: 10.0 ± 1.6, AMA: 8.0 ± 1.5). The most frequently consumed supplements included: protein powders, branch chain amino acids, vitamin C, omega 3 fatty acids, multivitamins and creatine (Table 4). Miscellaneous supplements included: iron tablets, chromium, tribulus, medium chain triglycerides, green tea extract, kelp powder, digestive enzymes, and L-carnitine. Protein and energy intakes from supplements as a percentage of total protein and energy consumed was 28.8 ± 15.7% and 16.3 ± 10.3%, and 22.4 ± 9.6% and 15.3 ± 6.0% for males and females PROS and AMAs, respectively.
Table 4 Self-reported Supplement Usage of British Natural Bodybuilders during Competition Preparation Caffeine, beverages, fluids and artificial sweeteners
There was no significant difference in reported caffeine intake (mg) in both sexes over time (male p = 0.732, female p = 0.467), between divisions (male p = 0.743, female p = 0.160), or interaction between time × division (male p = 0.558, female p = 0.423). Caffeine intake among males was: start PRO 236 ± 89 mg, AMA 210 ± 131 mg, mean 217 ± 120 mg; middle PRO 236 ± 89 mg, AMA 217 ± 130 mg, mean 222 ± 120 mg; end PRO 232 ± 83 mg, AMA end 229 ± 149 mg, mean end 230 ± 134 mg. Total caffeine intake among females was: start PRO 313 ± 67 mg, AMA 198 ± 98 mg, mean 233 ± 103 mg; middle PRO 313 ± 67 mg, AMA 212 ± 120 mg, mean 243 ± 114 mg; end PRO 313 ± 67 mg, AMA 237 ± 115 mg, mean 260 ± 106 mg. Caffeine intake scaled for body mass increased significantly over time in males (p = 0.021) and females (p = 0.026), however there was no difference between divisions (male p = 0.927, female p = 0.435), or interaction between time × division (male p = 0.407, female p = 0.204). Caffeine intake scaled for body mass among males was: start PRO 2.5 ± 1.1 mg/kg BW, AMA 2.4 ± 1.5 mg/kg BW, mean 2.4 ± 1.4 mg/kg BW; end PRO 2.9 ± 1.1 mg/kg BW, AMA 3.1 ± 2.1 mg/kg BW, mean 3.0 ± 1.9 mg/kg BW. Caffeine intake scaled for body mass among females was: start PRO 4.8 ± 1.2 mg/kg BW, AMA 3.1 ± 1.5 mg/kg BW, mean 3.6 ± 1.5 mg/kg BW; end PRO 5.5 ± 1.5 mg/kg BW, AMA 4.3 ± 2.1 mg/kg BW, mean 4.6 ± 1.9 mg/kg BW.
There was no significant difference (χ2 (1) 2.60, p = 0.11) between male PROs (87.5%) and AMAs (56.0%) in artificial sweetener usage. Among females there was a non-significant trend (χ2 (1) 3.75, p = 0.053) for AMAs (85.7%) to use sweeteners more than PROs (14.3%). There was no significant difference (χ2 (1) 0.083, p = 0.774) in sugar free cordial intake between male PROs (37.5%) and AMAs (32.0%). Furthermore, there was no significant difference in (χ2 (1) 0.44, p = 0.506) cordial usage between female PROs (20.0%) and AMAs (37.5%). There was also no significant difference amongst male competitors in daily servings of: coffee PRO 3.0, AMA 2.2, (χ2 (5) 4.69, p = 0.455); tea PRO 0.0, AMA 0.4, (χ2 (5) 2.42, p = 0.788), herbal tea PRO 0.8, AMA 0.6, (χ2 (5) 8.354, p = 0.138); sugar free carbonated energy drinks PRO 0.1, AMA 0.3, (χ2 (2) 1.34, p = 0.513); or sugar free carbonated beverages PRO 0.5, AMA 0.6, (χ2 (6) 3.82, p = 0.701). Amongst females there was no significant difference in daily servings of: coffee PRO 2.0, AMA 2.1, (χ2 (5) 3.11, p = 0.683); tea PRO 1.0, AMA 0.5, (χ2 (5) 2.42, p = 0.627); herbal tea PRO 2.0, AMA 1.2, (χ2 (5) 8.354, p = 0.382); sugar free carbonated energy drinks PRO 1.1, AMA 0.3, (χ2 (2) 1.34, p = 0.231); or sugar free carbonated beverages PRO 0.2, AMA 0.6, (χ2 (6) 3.82, p = 0.304). Finally, there was, a non-significant trend (t(29) 1.89, p = 0.068) for male PROs to consume more fluids than AMAs (PRO: 5.7 ± 1.3 L, AMA: 4.5 ± 1.5 L). However, there was no significant difference (z = 1.09, p = 0.273) in fluid intake between female PROs (median = 4.0, IQR 3.5–6 L) and AMAs (median = 3.5, IQR 3–4 L).