Not that I'm saying you should have to have your bbq without any meat ... sacrilegious I know! But balancing it out by serving some healthy vegetarian side dishes will do everyone a favour, not just those trying to eat healthily.
Corn on the cobs, jackets potatoes, sweet potato wedges and salads all make great bbq sides. This tasty lemony Ottolenghi rice salad, that I made with half wild, half basmati rice, also went down well with guests at our bbq as a nice alternative to the less healthy potato salad.
Puddings also tend to be sugar/cream laden affairs, but some strawberries and greek yoghurt always make for a luxurious tasting yet healthy pud. I was also delighted with the barbecued banana I was served, as a super sweet and yummy pudding without any of sugar or fat. Just put them on the bbq, with skins on, once you've finished cooking the meat and leave for 10 - 20 minutes whilst you eat your main course, until the skin goes black. Then just slice the skin lengthwise and serve with a spoon OR for a slightly more decadent treat, slit the skin and add a square of plain chocolate to each and allow to melt before serving ... yum!