N.P.
Your doctor is correct. Dripping sweat can be a major problem for bigger people, or anyone else who has grown unusually large (like some athletes). When you put on weight (fat or muscle), you don’t add sweat glands. As a result, those with bigger frames have a lower density of glands at the surface of their skin, with more space between each one. That means their perspiration won't cover their bodies as evenly, and they'll have to increase their sweat output to compensate. Large people also sweat more because it takes them more energy to move around. When people sweat too much, the moisture can form into rivulets and pour off, leading to dehydration and overheating. Always re-hydrate!
The thinner he gets, the more efficient his body will get at cooling itself, but even then... everyone sweats. I've also read that heredity could be a factor in how much or little someone sweats.