Throughout each dive, subjects performed a 20-minute long mild exercise on an underwater bike. The depth of dive was set at 15 meters, where the subjects performed an activity guided by Borg CR-10 scale at intensity level 3 (25 rpm). The ascent rate was set at 10 m/min, with a decompression stop at 5 meters for 3 min, according to the US Navy Manual Diving Table. 48 h prior to the immersions, none of the participants consumed medications or dived or flew. In the first part of the experiment, all subjects performed a dive breathing Enriched Air Nitrox (EAN, 32% ppO2). Baseline clinical measurements were collected before and after this first dive in order to have a reference [CTRL] and to measure physiological modifications due to immersion [NTRX]. After twenty days of no diving activity, subjects were engaged in a KD for seven days. At the end of this period, subjects performed a single immersion breathing EAN. The measures were performed after this single dive [KETO-NTRX]

Diet consisted of a very low carbohydrate ketogenic diet (for 7 days) with the use of some phytoextracts as previously described. The consumed diet was primarily made of beef and veal, poultry, fish, raw and cooked green vegetables without restrictions, cold cuts (dried beef, carpaccio and cured ham), eggs and seasoned cheese (e.g., parmesan). The allowed drinks were infused tea, moka coffee and herbal extracts. The foods and drinks that subjects had to avoid included alcohol, bread, pasta, rice, milk, yogurt, soluble tea, and barley coffee. To facilitate adherence to the nutritional regime, a variety of special meals based on protein and fibers were given to each subject. KD characteristics are protein intake 1.3g/kg/day, to maintain skeletal muscle mass; carbohydrates intake less than 40 g/day and 50-60% of total kcal to induce ketosis. In accordance with a hypocaloric profile, total energy intake was calculated with 200 kcal more than basal metabolic rate.

8-OH-dG (ng ⋅ mg-1 creatinine) and 8-iso-PGF2α (ng ⋅ mg-1 creatinine)

IL-1β (pg/ml), IL-6 (pg/ml) and TNF- α (pg/ml)

Kilogram (Kg)