Not an odd question at all. As a large man myself, I constantly find myself on the lookout for ways in my portrait business to help people look their best (no particular order... just as they came to mind):
- No broad lighting. This is a 'basic' for portrait lighting, but I'm always amazed when I see inexperienced photographers who simply throw light all over the place and don't seem to understand that broad lighting makes faces rounder and short lighting 'sculpts' the face...
- Rotate the subject 45-degrees to the camera. This, in combination with short lighting can dramatically de-emphasize a person's size.
- If the subject is sitting have them lean forward. I always tell subjects to 'lean over their belt buckle.' This natually de-emphasizes the belly, and provides elongation of the neck without specifically asking a subject to stretch their neck (that often causes subjects to really stretch, which always ends up looking awkward).
- Arrange the legs. There's a whole 'science' to positioning legs, but one of the most basic things to do for female clients is have them place one foot in front of the other, put all the weight on their back foot, and bend both knees slightly. (Check out any picture of a female celeb on the red carpet to see this in action... They all do it. Good media trainers!)
- Hide the gut. Portrait photography has a long tradition of putting the more... rotund... subject behind something to hide the belly. Whether it's another subject ("All them kids are finally good for something!" Actual customer quote during a session of mine. All in good fun, of course... I hope.), or an actual object. Get creative.
- Hide the gut, Part 2. Lay the subject down. Great way to hide a multitude of problems.
- The ol' vignette. I find the vignette is a great post-production tool for directing the eye towards the most important part of the picture- the face.
- The liquify tool. If you're a Photoshop user, the Liquify tool can be great for shrinking muffin-tops, saggy arms, etc. Plently of 'sin' is committed with the over-use of Liquify, but used subtly it can be a great addition to the toolbox.
- Darkness favors the big subject. I'm generally very hesitant to light a subject high-key if they're big... Unless the bigness is the point of the picture (A.K.A. you're photographing a pregnant lady, or a sumo warrior). Dark backgrounds and purposeful shadows can have a surprisingly large (har har) slimming effect.