Making weight in sport

Making weight is a global term for the targeted reduction of body mass, which is purported to enhance performance in aesthetic, gravitational and weight restricted sporting events. This process can be achieved via both chronic (across months and weeks) and acute (across days and hours) time frames, dependent on the specific context requirements of the competitive event (1). For example, aesthetic athletes may reduce body mass chronically, with the goal of altering specific body compositional tissues and therefore leading to an improved physique. However, certain combat sport competitors may opt to adopt acute practices to alter body mass for a specified weight category, with the aim of gaining competitive advantages in limb length and/or power to mass ratios over other opponents.

Sports in which body weight and composition play an important role

The chronic phase of making weight

During a chronic phase of body mass manipulation, the key goal is to modulate the various body compositional tissues, most notably centred around a reduction fat mass. Whilst there are benefits to the storage of fat mass in certain sporting environments, a decrease in this tissue can lead to a greater emphasis of a lean physique in aesthetic events, with improved mechanical efficiency and anthropometric characteristics for those in gravitational and weight restricted events. To that end, it is crucial that a well standardised and accurate assessment of body composition is established, in order to examine the specific amounts of tissues that can be modulated.

As a very general rule, it has been suggested that fat mass should not be reduced below a relative value of 6% in males and 12% in females. Where there is a requirement to reduce body mass beyond these limits, losses in fat free mass may also be required (Please note that these figures may be highly individual and 8% and 14% could already be too low for some individuals and 5 or 11% may be fine in others).

It is important to note that many methods are not accurate enough to use such specific cut-offs and how the percentage body fat is established and what method was used is important. When prescribing nutritional interventions for chronic weight making practices, it may help to assess resting metabolic rate (RMR). Recent research has highlighted that relative daily macronutrient compositions of 3g carbohydrate/kg , 2g protein/kg and 1g fat /kg, can be employed to effectively meet this RMR EI requirement in weight restricted athletes, in order to maintain health and performance (2).

Different weight making methods

The acute phase of making weight

In the acute phase of making weight, there are a number of methods that can be employed to artificially reduce body mass, inclusive of reductions in endogenous glycogen, gastrointestinal and total body fluid content (3). Practices inclusive of low carbohydrate, low residue, low fibre and low sodium diets all have the potential to reduce skeletal muscle/liver glycogen, faecal gastrointestinal bulk and associated bound water, resulting in losses of body mass without the need to reduce exogenous fluid intake or increase the capacity to sweat, techniques which are often associated with weight restricted sports (i.e. combat sport athletes, jockeys). Where the latter methods of manipulating total body fluid content are employed, particularly when utilising heated environments, care must be taken to monitor individual responses given the known effects that both hypohydration and hyperthermia can have on health and performance outcomes (4).