It is very likely that he has obstructive sleep apnea, as he puts on weight these 2 years and he snores louder since then.
Get your doctor to refer him to do a diagnostic sleep study test and follow up with a sleep specialist and an otolaryngologist (ENT specialist).
Treatment options:
1. CPAP therapy - most common and high successful rate, also eliminate snoring
2. Dental device (mandibular advancement) - works for mild and moderate patients, also eliminate snoring and bruxism
3. Surgery (tonsillectomy) - for some patients, there is risk always, lower successful rate
4. Weight management - yes, go exercise and lose weight
5. Avoiding alcohol close to bedtime - helps a little bit for mild patients
6. Avoiding sleeping in supine position (sleeping on his side) - helps when his snoring is due to supine related sleep apnea