This lesson consolidates the six acute weight cutting methods presented in the AETF webinar into a reference format. For each method, you will find a summary of the physiological mechanism, the typical weight loss range, the recommended timeline, and the key risks. A summary table appears at the end.

1. Low-Residue Diet (Fibre Restriction)

What it does

Reducing dietary fibre decreases the contents of the gastrointestinal tract. Less food residue in the gut means less weight on the scales. This is not fat loss or fluid loss; it is simply a reduction in the mass of material passing through the digestive system.

Typical weight loss

0.5 to 2% of body mass. The effect depends on the athlete's usual fibre intake. Someone already eating a low-fibre diet will see a smaller change.

Timeline

Begin 2 to 4 days before the weigh-in. Reduce fibre intake to 10 to 15 g/day.

Key risks

No significant adverse effects in the short term. Constipation is possible. Carbohydrate intake can remain high throughout, which is an advantage for training quality.

Foods to limit

• Whole-grain breads, cereals, rice and pasta
• Legumes
• Berries with skins, fruit peels
• Raw vegetables, potato skins
• Gristly meat, fish skin
• Quorn, hummus, popcorn
• Nuts, seeds, dried coconut

Foods to favour

• White low-fibre bread, low-fibre cereals
• White rice and pasta
• Meat, fish, poultry, eggs
• Berry or fruit juices without pulp
• Canned fruits
• Cheese, yoghurt, quark
• Soft tofu
• Seedless tomatoes, cooked carrots and beets
• Lettuce, cucumber, zucchini
• Smooth nut butters, oils

2. Glycogen Depletion

What it does

Carbohydrate is stored in the muscles (350 to 700 g) and liver (80 to 100 g) as glycogen. Each gram of glycogen binds approximately 3 g of water. Depleting glycogen stores therefore reduces both the glycogen itself and the water bound to it.

Typical weight loss

Approximately 2% of body mass. The effect is smaller if carbohydrate intake is already low before restriction begins.

Timeline and methods

• Restrict carbohydrate intake to less than 50 g/day for up to 7 days
• Combine with exercise to accelerate glycogen depletion
• Training combined with 50 g CHO/day for 7 days produced approximately 2% weight loss (Reale et al. 2017b)

Key risks

Full glycogen replenishment takes 20+ hours even with aggressive carbohydrate reloading. This method therefore demands careful recovery planning and more advanced nutritional knowledge. Training quality will decline during the depletion phase.

3. Sodium Restriction

What it does

Reducing sodium intake leads to decreased water retention and a corresponding weight decrease. The mechanism is straightforward, though no studies have directly measured acute weight loss from sodium restriction alone.

Typical weight loss

1 to 2% of body mass (estimated). The effect is minor if the athlete's sodium intake is already low.

Timeline

3 to 4 days of sodium restriction at 500 mg Na/day or less (equivalent to 1.25 g salt or less) (Sullivan & Lennon 2023). Note that sodium secretion decreases within days; within 7 days, secretion matches the new lower intake, reducing the ongoing effect.

Key risks

Ricci et al. (2025) advise caution about dropping below 2300 mg Na (5.75 g salt) for athletes. This method requires practical effort: preparing food yourself, using salt-free ingredients, checking spice mixtures for hidden sodium, avoiding sauces, condiments, sports drinks, and electrolyte products.

4. Water Loading and Fluid Restriction

What it does

A period of high fluid intake (water loading) suppresses antidiuretic hormone and increases urine output. When fluid intake is then sharply restricted, urine output remains elevated for a period, producing a net fluid loss greater than fluid restriction alone.

The evidence

Reale et al. (2018) tested a protocol in combat sports athletes:

• Intervention group: 3-day water loading at 100 ml/kg/day (e.g. 7000 ml for a 70 kg athlete) followed by 1-day fluid restriction at 15 ml/kg/day
• Control group: 1-day fluid restriction only
• Both groups followed a reduced-residue diet, mild energy restriction, and controlled sodium intake
• Result: the intervention group lost 3.2% of body mass vs. 2.4% in the control group
• No impact on performance measures (isometric strength, countermovement jump, repeated sprint ability)

Typical weight loss

1 to 3% of body mass, depending on the protocol. The key finding: fibre restriction for 4 days, a mild calorie deficit, and 1 day of fluid restriction alone produces approximately 2.4% loss. Adding 3 days of water loading provides an additional 0.8%.

Lighter protocols

Possible variations include 1 day of water loading instead of 3, and 80 to 90 ml/kg/day instead of 100 ml/kg/day.

5. Sweating (Active and Passive)

What it does

Sweating removes water from the body. Active sweating uses exercise. Passive sweating uses external heat sources such as saunas, hot baths, or hot showers.

Active vs. passive

Passive sweating spares glycogen stores and places lower physiological demands on the body compared to exercise-based sweating. Men's sweating response is generally greater than women's.

Typical weight loss

• 3% or less: a mild fluid deficit, achievable within 1 to 3 hours, recoverable within 4 hours or less (Reale et al. 2017b)
• Over 3%: moderate dehydration, requires longer recovery time

Recovery windows

Sullivan & Lennon (2023): if 2 hours or less from weigh-in to performance, limit sweat-based losses to 0 to 2%.

Passive protocol example

Connor & Egan (2021) tested a protocol combining 24 hours of calorie, carbohydrate, fibre, and fluid restriction with 2 hours of passive sweating (20 minutes hot bath followed by 40 minutes wrapped, repeated twice). Total loss was 4.54% of body mass. With 20 hours of recovery, participants regained 4.21%, but all were still dehydrated at the end of the recovery period.

Key risks

Sullivan & Lennon recommend medical oversight for sweat-based protocols. Ricci et al. (2025) advise monitoring core body temperature to prevent overheating above 40 degrees Celsius. Passive sweating carries real danger if unsupervised or taken to extremes.

6. Low Food Weight and Early Timing of the Final Meal

What it does

Eating low-weight foods in the 24 hours before weigh-in minimises the mass of food currently in the digestive system. This is often combined with the low-residue approach.

Risk level

This sits at the lowest end of the risk spectrum. The webinar flow charts list it alongside low-residue diet and gradual body fat reduction as the safest methods available.

Methods and Effects Summary