To offer insight in this area, we performed literature searches combining key terms such as “weight loss” and “combat sports” as well as individual sport names using relevant databases (e.g., PubMed, MedLine, Web of Science). Because of space constraints, it is not possible to review all the relevant literature in this area. However, contemporary articles that we considered the most informative are summarized in Table 2. The consistency of approach used to summarize the findings differs between articles because of methodological differences between studies. Nevertheless, as expected from the culture of weight-making sports, common approaches to making weight included skipping meals, fasting, saunas, sweat suits, laxatives, diuretics, diet pills, and vomiting. These weight loss strategies are prevalent across all the combat sports examined and are not just specific to certain sports.
As with any intervention, the first stage should always be to conduct a sound athlete assessment that is based on reliable and valid assessment tools. Although dual-energy x-ray absorptiometry is now beginning to replace hydrodensitometry as the reference method for studies of body composition in athletic populations (59), a limitation of this technique is its expense and exposure to low-dose ionizing radiation. In a sporting context, therefore, more practical methods, such as skinfold assessments and subsequent use of prediction equations to estimate percent body fat and lean body mass, are more commonly employed (21,22,59,60).
It is also important to estimate the typical daily training expenditure, and in this instance, measurements of heart rate provide the most user-friendly method (27). Having obtained relevant baseline physiological data, dietary analysis should then be conducted by a suitably qualified individual so as to identify nutritional habits that can be improved. Only then can a sound nutritional and conditioning program be developed to attempt to attain the target weight loss in the relevant period. It is difficult to provide precise recommendations in the present article because every athlete will present a different scenario. Nevertheless, we advise a daily energy intake that is at least equivalent to RMR (and as discussed in later sections, an increased protein intake) and a target weight loss of 1–1.5 kg/wk so as to avoid any loss of lean mass and decline in RMR (9,71).
The regulation of substrate utilization during exercise and feeding is a long-standing research area among biochemists. In contrast to the traditional glucose-fatty acid cycle (58), it is now generally accepted that fat oxidation during exercise is largely controlled by carbohydrate (CHO) availability given that insulin attenuates lipolysis so much so that it appears to limit fat oxidation (34). Furthermore, the suppressive effect of pre-exercise CHO ingestion on rates of lipolysis and lipid oxidation can persist for up to 4 hours after a meal (46). In this regard, ingestion of CHO, which ranks low to moderate on the glycemic index (and thus induces a low insulin response), does not attenuate lipolysis and lipid oxidation as much as those CHOs that are high glycemic (83).
In addition to pre-exercise feeding, it is also important to appreciate basic substrate utilization during exercise of varying intensities and duration. Early studies using stable isotope methodology demonstrated that lipid oxidation is reduced, whereas CHO utilization predominates at intensities above 65% o2max (62,77). Moreover, as exercise of moderate intensity becomes more prolonged, there is an increased reliance on plasma free fatty acids derived from adipose tissue lipolysis and reduced reliance on CHO sources (62). The precise cellular mechanisms regulating this shift in substrate utilization are beyond the scope of this review. In brief, evidence suggests that the increased glycolytic flux associated with high-intensity exercise limits the availability of free carnitine, which in turn reduces the activity of carnitine palmitoyl transferase (CPT1), the rate-limiting enzyme for transport of long-chain fatty acids (LCFAs) across the mitochondrial membrane (77).
Similarly, when rates of glycolytic flux are reduced, such as when muscle glycogen availability is progressively reduced during prolonged exercise, free carnitine availability is not as drastically compromised, and consequently, LCFAs are more readily transported into the mitochondria for oxidation (61). Although lipid oxidation appears to be increased in conditions of reduced CHO availability, it is important to note that amino acid oxidation also increased (43). Over time, this may lead to a loss of lean mass (35,45), which would likely be disadvantageous for the combat athlete (given the role of lean body mass in generating force), unless of course (and although not advised) the athlete is required to lose muscle mass to make the target weight class (48).
Finally, it is also important to note that fat storage in the postprandial period is increased with successive meals throughout the day (63). Such findings are likely because of the accumulation of successive insulin increases, increased esterification, and increased lipoprotein lipase activity such that adipose tissue becomes primed for storage (as opposed to hydrolysis) of fat as the day progresses. As a result, fat storage after a meal is greatest in the hours after the evening dinner meal when compared with breakfast and lunch (63). To compensate for this effect, it is advised that the training load is spread out over 2–3 sessions per day, as opposed to a single session of longer duration, so that there is continual interplay between substrate utilization and storage. In practice, this is often structured as an early morning run designated for fat burning, a late morning/early afternoon sport-specific technique/fitness session, and an early evening strength and conditioning session (48).
In considering the information presented above, it appears that timing, quantity, and composition of the macronutrient intake are all critical factors to consider when devising weight-making strategies. Nutritional practices should therefore be devised according to the structure of the daily training sessions so as to maximize the capacity for lipid oxidation during both exercise and recovery while also minimizing fat storage throughout the day.
Logical strategies to implement therefore initially center on a diet that is based around reduced (but we stress not zero) carbohydrate intake (given the role of CHO in regulating lipid metabolism), especially as the day progresses and also reduced saturated fat intake. In fact, there is now a growing body of literature from our laboratory and others demonstrating that training in conditions of reduced CHO availability actually enhances the oxidative capacity of skeletal muscle (47,85), as opposed to traditional guidelines surmising that daily training should be supported with high CHO intake.
When CHO is consumed, it is recommended that it is low glycemic, and in the case of pre-exercise, CHO ingestion, approximately 3 hours before exercise, is advised so as to minimize the suppressive effect of insulin on lipolysis. With the combination of intense training and reduced CHO intake, it is likely that many training sessions will be commenced with muscle glycogen stores that are not considered full or optimal for the energy requirements of the particular session. Given the capacity for such conditions to increase amino acid oxidation, it follows that the daily diet should increase protein intake so as to maintain (or at least minimize) any associated lean mass loss by maintaining the amino acid pool. In fact, we (48) and others (45) have shown that elevated daily protein intake can maintain lean mass even in the face of high daily training energy expenditure and when total daily CHO intake is reduced.
Where protein supplements are being used to support daily protein intake, it is also worth using a supplement that is both casein and whey based so as to minimize the suppressive effects of insulin on lipolysis (given that casein exerts a less pronounced insulin response than whey) (76) as well as increase feelings of satiety by inducing a prolonged feeding effect (33).
When considering the timing of training sessions, performing sessions solely dedicated to the purpose of fat burning are best performed in the early morning after an overnight fast and at moderate intensity and duration (34). In this way, the negative effects of pre-exercise meal ingestion (i.e., high plasma insulin concentrations) and high exercise intensities (i.e., high glycolytic flux limiting LCFA transport) are negated and the exercise stimulus is more closely aligned to maximizing lipid oxidation. In fact, recent data have suggested that fasted training (i.e., training before breakfast), as opposed to training after breakfast, enhances training-induced adaptations of skeletal muscle and may improve insulin sensitivity (78,79). Furthermore, data also demonstrate that fat oxidation was reduced by 30% during an 8-hour recovery period when CHO was ingested before exercise, as opposed to that ingested after exercise (64). For those sessions that are more dedicated to developing technique and sport-specific fitness (and hence are usually of much greater intensity), it is best to undertake them at least in the early morning, late afternoon, or evening time so that some liver and muscle glycogen is available (albeit not considered full) as a result of breakfast, lunch, and dinner ingestion, respectively. In such situations, it is again important to maximize potential lipid oxidation (despite the high exercise intensity) by attempting, if possible, to ensure that the last meal ingested before exercise is done several hours before and is always low glycemic.
It is difficult to provide exact recommendations in terms of the amount and percentage contribution of each macronutrient toward total energy intake that should be consumed. This is especially true considering the importance of individualized recommendations given that every athlete presents a different scenario in terms of RMR, target weight loss, daily training energy expenditure, time to achieve target weight, and so on. As documented earlier, a sound athlete assessment is the first stage that should be undertaken before devising and implementing any intervention. Indeed, in our experience, we have achieved success with daily CHO and fat intake varying from 2 to 5 and 0.5–1 g/kg body mass, respectively. Although current guidelines for daily protein intake are often controversial, in the case of making weight, we usually advise 2–2.5 g/kg body mass owing to the requirement to maintain lean mass in the face of daily energy deficits.
In considering the culture of combat sports where athletes tend to use weight-making methods relying on acute and chronic dehydration, emphasis needs to be placed on coach and athlete education so as to develop a training culture that promotes hydration before, during, and after training. In this regard, performing regular but simple measures of hydration status (such as monitoring training-induced acute weight loss, urine color and osmolality, and hemoglobin and hematocrit status) as well as monitoring habitual drinking patterns are useful educational tools to change athlete and coach perceptions. In instances such as professional boxing where there is typically >24 hours between the weigh-in and competition, an intentional dehydration-induced weight loss in the hours preceding the weigh-in may not be that problematic in terms of health or performance decrements. However, such instances should be carefully supervised by suitably qualified personnel so as to ensure that athlete safety and appropriate refueling and hydration strategies are administered. In combat sports where competition proceeds weigh-in by several hours, acute dehydration may not be appropriate as the short timescale may not allow for optimal refueling and hydration, which could therefore result in impaired performance (14,70). Further research to establish safe levels of acute dehydration in terms of athlete safety and impacting performance is required before definitive guidelines can be provided.
Finally, when devising nutritional and training interventions for combat athletes that simultaneously make weight, improve fitness and develop technique, limiting factors are often the structure of the athlete's day in terms of when coaches schedule training sessions and also whether the athlete is full-time or alternatively, have other daily commitments related to employment and family responsibilities, etc. Considering such limitations, effective communication and a multidisciplinary approach among support staff (e.g., the technical coach, strength and conditioning coach, sports nutritionist) are required so as to develop the best-case scenario in relation to the particular athlete.
In addition to the nutritional strategies described above, there are also a number of supplemental strategies that may help to aid weight loss and perhaps more importantly maintain immune function during times of intense training when energy availability is reduced. The latter is particularly important for those athletes whose dietary preferences may prevent them from obtaining key macro- and micronutrients from food choices per se. Unfortunately, empirical evidence supporting these supplements, especially in athletic populations, is limited, and practitioners are often left to base their decisions on anecdotal reports. A review of potential supplements is shown in Table 3.
On the basis of the principles described herein, we have recently published a case study account (48) outlining a nutritional and conditional strategy designed to help a male professional featherweight boxer (57 kg) make weight for a new weight division of super featherweight (59 kg). Over a 12-week period, the client athlete adhered to a daily diet approximately equivalent to his RMR (6–7 MJ; 40% CHO, 38% protein, and 22% fat). Average body mass loss was 0.9 ± 0.4 kg/wk, equating to a total loss of 9.4 kg. This weight loss resulted in a decrease in percent body fat from 12.1 to 7.0% (Figure). In the 30 hours between weigh-in and competition, the client consumed a high-CHO diet (12 g/kg body mass) supported by appropriate hydration strategies and subsequently entered the ring at a fighting weight of 63.2 kg.
This nutritional strategy represented a major change to the athlete's habitual weight-making practices and did not rely on any form of intended dehydration during the training period or preceding weighing-in. However, in this instance, it was evident after baseline assessment that the athlete would have to lose muscle mass to make the target weight. Nevertheless, we suspect that this is commonplace for many combat athletes (who do not have scientific input from support staff), but they have never had the knowledge that lean mass will be compromised.
In fact, following continual coach and athlete education, this athlete has now moved up another weight division to lightweight (61.3 kg), 9 lb heavier than when he won his first domestic national title and also held a version of the world featherweight title. With improved food choices when out of training, this particular athlete now reports to the beginning of training camps no more than 5–6 kg over his competitive weight. As such, the target weight is now achieved with greater ease and in a shorter duration. In some instances, we have also used acute intentional dehydration of 1–1.5 kg in the hours preceding weigh-in with no performance decrements or symptoms of ill health.
The present article has attempted to outline how adhering to basic principles of metabolic regulation that emphasize timing, composition, and quantity of energy intake can help inform nutritional and conditioning programs to strategically make weight. Based on these principles, we provide an overview of guidelines in Table 4 where we pay particular attention to timing and composition of meals in relation to the structure of a combat athlete's training day. For illustrative purposes, we base our plan on a professional boxer who may train 3 times per day thought it is important to note that every athlete presents an individual scenario.
In addition to the published case study outlined in the previous section, we have used similar approaches with professional boxers ranging in weight division from flyweight to heavyweight (in the latter case, to change body composition and not necessarily mass) and observed positive results. Essentially, it is through continual education of both coach and athlete and also the willingness of both parties to adopt novel practices, which is crucial to the success of these interventions. Given the lack of research in this area, we consider it vital that similar case study–type accounts from other combat sports are published in the scientific literature. It is only through sharing such information that the safety and performance of combat sport athletes can be enhanced.
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