I follow a similar diet to keep my weight & type 2 diabetes under control. I understand what you mean about these things typically being very carb-heavy. Even the 'healthy' fruit platter that is offered for dessert is often tropical fruit - pineapple, mango, etc. - that I'd love to eat but really shouldn't, or the 'plain' protein is chicken in a sticky glaze or something, while any salad that I might normally eat by the bucket-load is limited to a bit of garnish round the sides. One of the difficulties is that as soon as you describe a low-carb diet to people it sounds a lot like Atkins and gets dismissed as faddy nonsense by many, or you get swept up by the Keto-police and accused of being a fraud if you don't count and fret over every last scrap of carbohydrate.
For me, this typically comes up at external events (hiring, training, conferences, education outreach, etc.) which happen maybe once a quarter. If it's just a day, I'll usually try to have a substantial breakfast, make sure I've got some low-carb snacks in my bag (e.g. nuts) to eat thorough the day so I don't starve and eat a minimal amount of the least 'bad' things at the buffet to join in with the social element. For a longer event, I would at least try to request a low-carb option if dietary requirements were solicited in advance, but go prepared with the backup nuts in case it didn't work out, and - if away from home - find a supermarket/convenience store to pick up a pre-packaged salad or similar to take along on day 2 if day 1 didn't work.
For a regular team event, I don't think it's unreasonable that you would raise with your boss/whoever orders the catering that the default isn't meeting your needs, and asking what scope there is to change the menu. They might be accommodating and have the caterers include some options that work for you in the overall menu and might be welcomed by others who don't relish the afternoon doze brought on by a lunch of refined carbs. They might have the caterers supply a big bowl of salad with 'reserved for User65535' written on it, to which you might say "thanks but no thanks" (or might cause others to ask for there to be enough salad for everyone in future), or they might tell you there's nothing they can do (which might be a brush-off or genuine - at some point, catering for lots of different diets becomes unmanageable for a voluntary event) - you won't know without asking. If it doesn't work out, there are low-carb options that you can prepare ahead to eat with fingers, or just a fork at most, and you should take these along and join the social event if that's what you'd otherwise do. If your food occasions some comment, you've got something non work-related to chat about if people are genuinely interested (if you make something more interesting than a basic salad, take a bit extra to offer a taste to interested people - perhaps this evolves into a pooled/"pot luck" lunch instead of a catered one) , or can bat away ill-informed/prying comments with "it's just the food I prefer to eat. Did anyone else get caught out in the crazy rain last weekend?" or similar - either way is better than being the person who appears to be isolating him/herself when the rest of the company are socialising.