We aimed to evaluate the effect of the Mediterranean diet (MD) compared with a 
prudent diet (PD) combined with physical activity on obese obstructive sleep 
apnoea syndrome (OSAS) patients who were treated with continuous positive airway 
pressure. 900 patients were evaluated and 40 obese patients (body mass index ≥ 
30.0 kg · m(-2)) who met the inclusion criteria, with moderate-to-severe OSAS 
(apnoea-hypopnoea index (AHI) >15 events · h(-1) and Epworth Sleepiness Scale 
score >10) based on overnight attended polysomnography, were included in the 
study. After randomisation, 20 patients followed the MD and 20 a PD for a 
6-month period. All patients were counselled to increase their physical 
activity. Concerning sleep parameters, only AHI during rapid eye movement (REM) 
sleep was reduced to a statistically significant degree, by mean ± SD 18.4 ± 
17.6 events · h(-1) in the MD group and by 2.6 ± 23.7 events · h(-1) in the PD 
group (p<0.05). The MD group also showed a greater reduction in waist 
circumference (WC) (-8.7 ± 3.6 cm), WC/height ratio (-0.04 ± 0.02 cm · m(-1)) 
and WC/hip ratio (-0.04 ± 0.03 cm · cm(-1)), compared with the other group (-2.6 
± 1.7 events · h(-1), -5.7 ± 3.8 cm, -0.03 ± 0.02 cm · m(-1) and 0.02 ± 0.02 cm 
· cm(-1), respectively; p<0.05). Our results showed that the MD combined with 
physical activity for a 6-month period was effective in reducing the AHI during 
REM sleep without any statistically significant effect in the other sleep 
parameters, compared with a PD in obese adults with moderate-to-severe OSAS.