Strategies for dehydration
There are three strategies that can be used to lose weight with dehydration: the consumption of less fluid (fluid restriction), the “unlocking” of bound body fluid that will in turn be excreted, and the promotion of additional fluid loss . Fluid restriction is an obvious means to reduce total body water by limiting the amount of liquid an athlete takes each day. Reductions in fluid compartments in the body can be derived from losses from both intracellular and extracellular stores and include free or bound water. Bound water, which has the potential to be eliminated, includes water in glycogen stores and also water into the intestinal space due to the presence of food matter with absorptive properties, such as fiber-containing foods. The excretion of water from the body is accomplished via respiration, urination, and sweating. The extent of fluid loss from specific tissue compartments, including the skeletal muscle, is not well understood but may depend on the strategy to lose weight with dehydration . A combination of exercise and heat reduces skeletal muscle volume in active muscles, whereas less active muscles maintain volume when dehydration is induced by exercise in heat.
Acute weight loss
To limit health risks, the competition weight should not be more than 5 percent lower than a healthy weight outside the competition season . The advice for athletes is to lose a maximum of about 3 percent of your body weight the last days before competition. This is a combination of fluid, carbohydrates and intestinal filling.
5 days before competition (or after heavy exercise) | low-carbohydrate – high-protein diet
The adoption of a low-carbohydrate diet (<50 gram/day) is an effective means to lose weight via the loss of carbohydrate reserves (glycogen) and bound water. Depleting the glycogen reserves can lead to body weight loss up to 0.75 kilogram (~1% body weight). Additional body weight loss of 2 kg (~2-3% body weight) is possible by losing bound water, as glycogen is stored in a hydrated form composed of 2.6 gram fluid per 1 gram of glycogen. To maintain muscle mass, daily protein intake should be increased to 2.0-2.5 gram per kg body weight.
2 days before competition | fiber intake restriction
A restriction of fiber intake (<10 gram fibre/day) can lead to weight loss of 0.5-1.0 kg (~1% body weight) in the last days before competition. The advice is to restrict fiber intake only the last two days before competition, as constipation can be a consequence of a longer low-fiber diet.
½ to 1 day before competition | fluid loss
Losing a small amount of fluid (up to 2 percent of the body weight) is possible without negative effects on performance. There are several methods to lose fluid within the last day before competition: eating low-sodium meals (<500 milligram/day), drinking little in the last 12 hours before weigh-in or losing extra weight by sweating (sauna, exercising with extra clothing or hot water bath). As the weigh-in is the day before competition, a slightly higher fluid loss might be possible but discuss this with a doctor and nutrition expert. However, in terms of health, it is important to highlight that a very high amount of fluid loss coupled with depletion of glycogen stores could be linked to thermal and metabolic stress, changes in enzyme activity, structural changes in muscles, altered central nervous system function and negative psychological effects .
Replenish after weigh-in
The optimal post weigh-in recovery strategies are influenced by the methods used to achieve acute weight loss. An athlete can try to replenish the lost fluid and glycogen in the period between the weigh-in and the competition. An ideal replenishment protocol ensures as much fluid and glycogen replenishment as possible, without feeling full or nauseated. A large amount of fluid (for example 10 milliliters per kilogram of body weight) immediately after the weigh-in, followed by small amounts of fluid until the competition, promotes gastric emptying. The addition of electrolytes or possibly some proteins ensures that the fluid is not immediately expelled again . An athlete can replenish the glycogen reserve by taking a carbohydrate-rich drink or food after the weigh-in. To prevent gastrointestinal problems, an athlete can choose small amounts of carbohydrates in liquid or compact foods .
The aforementioned recommendations provide general guidelines for acute weight loss, but there is a need for an acute-weight-loss plan for each athlete individually. Counsel a nutrition expert to assist with a tailored pre-competition nutrition plan. In addition, the advice is to practice weight-loss strategies before participating in competitions.
- Reale R, Slater G, Burke LM. Acute-Weight-Loss Strategies for Combat Sports and Applications to Olympic Success. Int J Sports Physiol Perform. 2017;12(2):142-151.
- Hackney KJ, Cook SB, Fairchild TJ, Ploutz-Snyder LL. Skeletal muscle volume following dehydration induced by exercise in heat. Extrem Physiol Med. 2012;1(1):3. Published 2012 Sep 4. doi:10.1186/2046-7648-1-3
- Burke LM, Slater GJ, Matthews JJ, Langan-evans C, Horswill CA. ACSM Expert Consensus Statement on Weight Loss in Weight-Category Sports. Curr Sports Med Rep. 2021;20(4):199–217.