Context : The MAGIC collaboration recently reported correlated X-ray and very high-energy ( VHE ) gamma-ray emission from the gamma-ray binary LS I +61 303 during \sim 60 % of one orbit .
These observations suggest that the emission in these two bands has its origin in a single particle population .

Aims : We aim at improving our understanding of the source behaviour by explaining the simultaneous X-ray and VHE data through a radiation model .

Methods : We use a model based on a one zone population of relativistic leptonic particles at the position of the compact object and assume dominant adiabatic losses .
The adiabatic cooling time scale is inferred from the X-ray fluxes .

Results : The model can reproduce the spectra and light curves in the X-ray and VHE bands .
Adiabatic losses could be the key ingredient to explain the X-ray and partially the VHE light curves .
From the best-fit result we obtain a magnetic field of B \simeq 0.2 G , a minimum luminosity budget of \sim 2 \times 10 ^ { 35 } \mathrm { erg s ^ { -1 } } and a relatively high acceleration efficiency .
In addition , our results seem to confirm that the GeV emission detected by Fermi does not come from the same parent particle population as the X-ray and VHE emission .
Moreover , the Fermi spectrum poses a constraint on the hardness of the particle spectrum at lower energies .
In the context of our scenario , more sensitive observations would allow us to constrain the inclination angle , which could determine the nature of the compact object .

Conclusions :