Hydration at the gym: what the reference values say and what they do not
There is no figure in the European opinions for "how much to drink during a workout". The EFSA reference values — 2.0 litres a day for women, 2.5 for men — apply explicitly only in conditions of moderate ambient temperature and moderate physical activity. Training is, by definition, outside that domain.
Where the figures come from and what they cover
The source is the opinion Scientific Opinion on Dietary Reference Values for water, published in EFSA Journal 2010;8(3):1459. It sets adequate intakes for total water intake: water you drink, all other beverages, and the moisture in food.
For adults: 2.0 l a day for women (95th percentile: 3.1 l) and 2.5 l a day for men (95th percentile: 4.0 l).
The detail that matters here: the opinion states that the values apply in conditions of moderate ambient temperature and moderate physical activity level (PAL 1.6).
We set out the values for all age groups in the article on the EFSA reference values.
Why there is no figure for exercise
Because the variables that matter are individual and situational: duration and intensity of effort, temperature and humidity in the room, clothing, individual sweat rate, acclimatisation.
Two people of the same weight, in the same gym, doing the same workout, can lose appreciably different amounts of water. A single figure for everyone would be an invention, not a recommendation.
Any material that tells you precisely how many millilitres to drink at minute 30 of your workout is selling you a certainty that does not exist in the reference documents.
What remains useful, in practice
Without making medical recommendations, a few things are purely descriptive and verifiable by anyone:
- Intake is spread across the day, not recovered in a single go. The reference values are daily, not per session.
- "From all sources" includes food. A significant part of intake comes from food and from beverages that are not water. Nobody reaches the reference value by counting bottles alone.
- Access matters more than intention. If the serving point is at the far end of the gym, consumption falls — whatever the person intended.
- Heat changes the equation. In summer and in crowded gyms, conditions leave the domain in which the reference values were established.
For individual questions — pregnancy, breastfeeding, medical conditions, medication, endurance exercise — ask a doctor. This is not an article of medical advice.
What a gym can do
The things that influence actual consumption are mundane and logistical:
1. Position of the serving point. On the natural route, not in a corner. 2. Availability at peak hours. A serving point that is empty at 7 p.m. does not, in practice, exist. 3. The container. If people have a bottle they can refill, they drink more often.
We wrote separately about choosing the container, in the article on reusable bottles.
What this article does not claim
It does not attribute health effects to any type of water and does not argue that water treated in a particular way is preferable for exercise. For molecular hydrogen there is no authorised health claim in the European Union.
Water contributes to the maintenance of normal physical and cognitive functions, at a daily intake of at least 2 litres from all sources.
Key points
- The EFSA values are daily, total, and valid only at moderate exercise and temperature.
- There is no official figure for consumption during training, because the variables are individual.
- Any material giving an exact figure for exercise goes beyond what the reference documents support.
- Physical access to water influences consumption more than recommendations do.
- Individual questions go to a doctor.
Sources
- EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA), Scientific Opinion on Dietary Reference Values for water, EFSA Journal 2010;8(3):1459, doi:10.2903/j.efsa.2010.1459
- EFSA, EFSA Journal 2011;9(4):2075, doi:10.2903/j.efsa.2011.2075
- Regulation (EU) No 432/2012 — EUR-Lex, CELEX 32012R0432
