This study is novel in providing insight on the nutritional strategies of high-level competitive natural bodybuilders. Although other studies have claimed to recruit high-level or elite natural bodybuilders, their definition of elite has been less stringent than the present investigation [3, 5]. We found no significant difference in dietary intake between the placed and DNP competitors. In spite of this null effect, results of practical significance testing suggest carbohydrate consumption in the early stages of contest preparation may influence competitive outcome in the male bodybuilders. We also report that high level natural bodybuilders consume more energy, particularly from carbohydrate than previous accounts of natural bodybuilders [3,4,5,6,7,8]. As bodybuilders approached competition, energy intake is reduced primarily through a reduction in carbohydrate and fat intake, with protein intake remaining constant throughout contest preparation. Accounts of body composition measurement show that bodybuilders often employ subjective methods to estimate BF% [17]. Finally, we report on supplement and caffeine intake and note high consumption compared to publicly prescribed safety recommendations for caffeine.

Body composition and the fat free mass index

Skin callipers were the most commonly used methods for estimating BF% amongst competitors, while subjective methods based on appearance were also reported. Objective measurements of BF% from competitive bodybuilders have been reported previously; these data suggest ranges from 4.1 to 10.9% and 8.6 to 11.3% in males and females respectively [2, 6,7,8, 19,20,21]. Interestingly in a sport concerned with achieving a low body fat, the majority of competitors did not report BF%, with a proportion using visual methods to estimate BF%. It is possible that the lack of reporting of BF% may reflect a greater emphasis placed on the appearance of low body fat in bodybuilding rather than objectively obtained measures.

A FFMI above 25 kg/m2 is suggested as an upper limit for muscle accretion, without the use of AAS [16]. This threshold, however, is based on photographic estimates of pre 1959 Mr. America bodybuilders and the objective measurement of 157 gymnasium users so should be interpreted with some caution [17]. We provided an estimate of the mean FFMI based on competitors who reported BF% using callipers of 22.7 kg/m2, this is higher than the 21.8 kg/m2 reported in the study of gymnasium users [16]. Interestingly, two male competitors in this study had a FFMI above the 25 kg/m2, (25.73 and 25.15 kg/m2) natural threshold based on the pre 1959 Mr. America winners. We did not measure FFM or BF% directly and we acknowledge the limitations of self-reported accounts of BF%; however, it is not inconceivable that there are high-level natural bodybuilders who exceed this theoretical FFMI 25.0 kg/m2 threshold. The mean FFMI of 18.1 kg/m2 reported in females was in agreement with previous estimates of 18.3 kg/m2 [21]. but greater than that of a recent case report [6]. No FFMI upper threshold has been proposed for females; however, a FFMI between 19.0 to 20.0 kg/m2 seems a reasonable objective starting point based on estimates of female populations [22].

Dietary intake

Energy intake

As expected energy intake of male and female competitors was higher at the start of contest preparation compared to the end. Similar findings have been reported in previous observations [13, 23, 24]. Competitors reported reducing energy intake in stages over the course of their preparation with smaller differences from the start to the middle and middle to end of the diet. Similar strategies involving modest reductions in carbohydrate and fat consumption to facilitate weight loss has been reported elsewhere [4]. In contrast, two case studies of bodybuilders [5, 7] reported a reduction in energy intake between 882 to 1300 kcal/d from the start to the end of the competition preparation, compared to smaller reductions (554 kcal/d) in our placed males. Smaller reductions are intended to counteract metabolic adaptations to dieting, changes in energy requirements and preservation of LBM [11]. Both male and female competitors reported a high meal frequency. This may reflect the practical aspects of consuming large volumes of food combined with and belief that multiple meals may preserve more LBM, while contributing to greater appetite control [25,26,27].

Research indicates greater LBM preservation and exercise performance with slower versus faster weight loss, a 0.5 to 1% of BW per week is recommended for natural bodybuilding [10, 28]. Our cohort reporting dieting for on average 24.9 and 23.3 weeks in males and females respectively, compared to 14 weeks in the study by Robinson et al. [5], and 26 weeks in both Rossow et al. [3] and Kister et al. [4] studies. The weekly weight loss in the present study was estimated to be 0.46% per week in the placed males, compared to 0.5 [3], 0.7 [4] and 1.0% [5] in case studies. Fascinatingly, Petrizzo et al. [7] recently advocated weight loss of 0.5% BW per week for LBM preservation during natural bodybuilding contest preparation. In the present investigation, weight loss was 0.46% per week reflecting this recommendation; it seems likely that slower weight lost in our placed males may have resulted in greater preservation of LBM than the DNP males.

Macronutrients

Carbohydrate

Carbohydrate was the most abundant macronutrient consumed across all the phases of the diet, in both male and female competitors. The majority of carbohydrates came from cereals, tubers, fruit, and vegetables. Confectionary items, such as sweets and water-based desserts, legumes and bread were consumed sparingly during contest preparations in agreement with previous accounts of bodybuilding menus [5, 7, 29]. Carbohydrate intake was reduced from the start to the end of contest preparation reflecting the practice seen in bodybuilding case studies [3,4,5]. Carbohydrate intake amongst placed males (5.1 g/kg BW) was similar to a meta-analysis of contest preparation bodybuilders (4.9 g/kg BW) [13]. However, intake was higher amongst placed male competitors in the weeks preceding the competition (end of the diet), 4.6 g/kg BW compared to previous reports (3.8 g/kg BW) [13]. Intake was also higher for male competitors compared to three recent case studies, where mean intakes were between 2.5 to 3.0 g/kg bw over 26 and 28 weeks [3, 4], and 1.2 to 1.4 g/kg bw over 14 weeks [5].

Carbohydrate energy in the female cohort (placed and DNP Start of diet: 3.7 and 4.0 g/kg BW), was higher than two case studies (3.4 g/kg BW [6] and 1.5 to 1.9 g/kg BW [7]) and a meta-analysis conducted on studies reporting intake amongst female bodybuilders over 30 years ago (3.1 g/ kg BW) [13]. Higher intakes have been reported in a recent case report of a dieting female physique competitor where intake was initially 5.0 g/kg BW [8] before decreasing to 1.8 g/kg BW by the end of the 6 month study period. Intakes of 5.0 g/kg BW have been reported in the final week of contest preparation, [13] which may reflect carbohydrate loading strategies in the final week of competition.

Carbohydrate intake amongst the placed males (4.6 to 5.1 g/kg BW) was in line with previous recommendations of 4–7 g/kg BW for bodybuilders aiming to maintain weight [30]. Cohens d effect size testing indicated carbohydrate intake at the start of the diet may have some impact on competitive outcome. Placed males consumed 1.0 to 1.4 g/kg BW more carbohydrate than those who DNP during this period. This equates to an additional 75 to 97.5 g carbohydrate (281.2 to 365.6 kcal) per day in a 75 kg male. This additional carbohydrate is a non-trivial amount as even modest resistance training protocols can deplete muscle glycogen concentrations between 24 to 82% [31, 32]. Furthermore, as little as 15 g of carbohydrate consumed during resistance training may increase performance in hypertrophy rep ranges [33]. Finally, the effect of isometric contractions on bodybuilders’ muscle glycogen concentrations should be considered. Bodybuilders routinely hold isometric contractions for between 6 to 60s for 10 to 30 min In preparation for competition [8]. By way of comparison 10 min of isometric exercise at 20% of maximum voluntary contraction for 10 s, with 10 s rest intervals can severely deplete muscle glycogen in type 1 fibres [34]. An adequate carbohydrate intake during contest preparation to maintain muscle glycogen should therefore be an important consideration for the natural bodybuilder.

Low carbohydrate diets are effective for weight loss, however they may result in a disproportionate loss of LBM [35,36,37,38]. An example of this can be seen in the study by Robinson et al. [5] where the athletes lost 43% of their LBM following a low carbohydrate diet. While higher carbohydrate diets utilised by other bodybuilding case studies resulted in smaller LBM loss, 21% and 32% [3, 4]. Multiple factors could have contribute to the LBM loss seen in Robinson et al. [5], however recent critiques have suggested more prudent dietary strategies should be employed for natural bodybuilding [7, 39]. Interestingly, the two female athletes involved in the Petzzaro et al. [7] and Rohrig et al. [8] case reports increased LBM and reduced fat mass in despite following a similar dietary approach to Robinson et al. [5]. With the exception of a case report which tracked the body composition of 6 physique athletes (4 male, 2 female) using AAS [40] increases in LBM and a reductions in fat mass amongst bodybuilders during contest preparations have been previously unreported [1, 3,4,5,6, 21, 41,42,43]. In spite of this finding evidently, there may be a threshold for carbohydrate intake, after which there is an increase in the rate of LBM loss regardless of protein intake or resistance training.

Protein

Protein constituted between 32.0 to 40.0% of total energy in both male and female competitor’s diets in the present study in line with previously reported data [12]. The main protein sources were from dairy, white meat, nuts and seafood in agreement with data from previous bodybuilding studies [5, 6, 29]. The high intake of protein from dairy reflects the prominence of protein powder in competitors’ diets. Red meat and eggs were consumed to a lesser extent than the aforementioned foods options. Protein intakes were between 2.7 g/kg BW and 3.3 g/kg BW amongst male and female competitors, similar to reports from case studies 2.2 to 3.5 g/kg BW [3,4,5,6,7,8].

The prioritisation of protein over other macronutrients during energy restriction is common practice amongst bodybuilders [3,4,5,6,7,8, 40]. High protein diets are known to spare LBM during energy deficits [43,44,45,46], maintain nitrogen balance and stimulate muscle protein synthesis (MPS) [47]. Protein is also satiating, which may improve dietary adherence during energy restriction [45]. Protein digestion is also known to have the greatest thermic effect of the three macronutrients. Approximately 20 to 30% of net energy is lost through dietary thermogenesis of protein (compared to around 3% for fat); this extra thermic effect may contribute to additional weight loss [36, 45].

Protein intake recommendations for strength-trained athletes during energy restriction are 2.0 g/kg BW, with 0.25 to 0.3 g/kg BW during the early recovery phase after exercise [48]. However, a recent systematic review has recommended higher levels of between 2.3 to 3.1 g/kg BW of LBM during severe calorie restriction [49], although this recommendation was based on only two empirical studies [36, 43]. Nevertheless it seems likely that protein intake amongst the competitors in this study was adequate for the preservation of LBM. This additional protein may be advantageous exploiting the thermic effect of food and satiation offered by additional protein. However, a recent experimental study found that additional protein energy was not realised in changes in body composition [37, 50].

Fat

Fat intake was the lowest amongst the three macronutrients, and like carbohydrate was reduced over time in favour of maintaining protein. There was a tendency for competitors in this cohort to favour low-fat diets. Food selection patterns emphasised this with oils and red and processed meats making up only a small percentage of the cohort’s overall diet. Although eggs were commonly consumed, the yolks were routinely discarded. Nuts and seeds, along with white meats, marine and cereals were the most prominent sources of fat in the athletes’ diet. Moreover, many athletes reported consuming an omega-3 fatty acid supplement, suggesting athletes favouring a diet higher in mono- and polyunsaturated fatty acids rather than saturates. Low fat food selection patterns have previously been reported [29].

The fat intakes recorded in the present study (start of diet: males 0.8 g/kg BW, females 0.8 g/kg BW) were similar to previous accounts reported by Spendlove et al. [13] for male (0.95 g/ kg BW) but higher than previous reports of female competitive bodybuilders (0.32 g / kg BW). Despite the seemingly low fat intake accounts as low as 8% of energy have been reported in the bodybuilding literature [51, 52]. Bodybuilder’s in the present study placed nutrients in a hierarchy, prioritising protein followed by carbohydrate for the aforementioned reasons. Low fat diets have however been cited to reduce testosterone concentrations during a calorie deficit [53, 54]. However, in a 11 week study of bodybuilders dieting for competition, plasma testosterone and IGF-1 concentrations decreased, despite subjects consuming a relatively high fat intake (energy 25% or (1.18 g / kg BW) [43]. Differentiating between the effects of fat and energy intake on hormone concentrations is clearly a challenge. The intakes recorded in this study in conjunction with high protein and high carbohydrate diets may therefore merit further investigation.

Finally, the low fat intakes seen here may reflect a paradigm shift between the present day, and the 1980’s and 90’s where the majority observational studies of bodybuilders were performed [13]. Likewise the results reported here may also reflect a difference in approach between British and American bodybuilders, with all six recent case studies opted for a higher fat approach [3,4,5,6,7,8].

Supplementation and caffeine intake

Male and female competitors routinely consumed between 5 and 7 supplements during contest preparation. Protein powders, multivitamins, BCAA and creatine were the most commonly consumed supplements in agreement with previous observations of gymnasium users, athletes and bodybuilders [55,56,57]. Whey protein was routinely consumed at breakfast and post resistance training. In contrast, casein-based supplements were commonly consumed as the last meal of the day. The use of protein in this manner suggests nutrient timing strategies, the effectiveness of which has been called into question [58]. Branch chain amino acids are used as means of maximally stimulating MPS over the course of the day by providing a bolus dose of BCAA every few hours along with or between meals, for the preservation of LBM in what is commonly referred to as a ‘pulsing strategy’ [47]. However when the muscle full effect is considered, the use of BCAA as part of a high protein diet may offer little if any additional stimulation of MPS [59]. Moreover, the daily doses of BCAA (30 g) and beta-hydroxy-beta-methylbutyrate (2 g), consumed by the athletes in the Kistler et al. [4] case study failed to prevent a greater loss of LBM compared to Rossow et al. [3].

Specialist fat burning and pre-exercise supplements were also popular amongst this cohort. Pre-exercise supplements often contained combinations of vitamins, minerals, amino acids, creatine, caffeine and lactate buffers usually in the form of beta alanine, citrulline malate and arginine. The efficacy of these individual ingredients have been reviewed for natural bodybuilding [11]; however, their use in combination is largely unknown. In addition, because caffeine is a prominent ingredient in many of these supplements, competitors should consider the contribution these supplements make to their caffeine intake. This point is particularly pertinent when considering competitors may often consume large amounts of energy drinks and hot beverages [5,6,7]. Indeed, several competitors exceeded the 400 mg per day safety consumption limits specified by The European Food Safety Agency for caffeine. Although these consumption limits are based on a 70 kg individual, competitors should be aware that intakes above 9 mg /kg BW may be ergolytic as well as having unintended side effects [60, 61].

Limitations

There are limitations with the method used to assess dietary intake, under-reporting of habitual dietary energy intake is estimated to be between 18 to 54% in non-bodybuilding populations [62]. In particular carbohydrates tend to be under-reported, while protein intake over reported [62]. Likewise, foods that portray a negative health image such as confectionary are often under reported while foods that portray a positive health image such as fruits and vegetables are over reported [62]. The prevalence of under- or over reporting within bodybuilding population is unknown, however bodybuilders are known for their strict adherence to dietary plans [3,4,5,6,7,8]. The dietary recall only incorporated a single day’s intake at three arbitrary time points. As a result, competitors largely reported their dietary intake for training days, while intake on non-training days is likely to be lower. This bias likely resulted in inflated values for energy intake, furthermore strategies such as carbohydrate and calorie cycling were likely missed by the single day recall method. Despite the limitations of the method used to capture dietary intake we were able to detect a reduction of energy intake over time. Moreover, a single day’s intake may have led to misclassification of dietary diversity, although the diet diversity scores are agreement with previous accounts of bodybuilding menus.

The BF% values used to estimate the FFMI of competitors are based on self-reported accounts using skin callipers. Competitors did not report if these skinfold test were carried out by trained professionals. Although, the values reported were plausible (essentially they match with the values reported elsewhere amongst competitive bodybuilders taken form objective measures) for competitors competing in a national competition, we omitted to include them in the report along with the subjectively obtain values as they should not be regarded as accurate.