Yes, we actually keep it locked up, out of sight, out of mind, and it's been very successful!
This started out as an ounce of prevention when we remodeled our kitchen--there were going to be a couple of lower cabinets in the little passage between the dining room and kitchen, out of the way of prep but very handy for wine and liquor. With our teens and their friends in and out of the house all the time, it seemed prudent. We like an occasional bottle of wine but cook more with liquor than drink it so locking all that up wasn't inconvenient at all.
It was so funny how I gradually started tucking sweets in there-- now the cabinets are jammed with candy of all kinds, granola and power/protein bars, treats stockpiled from clearance and specials, baking chocolate and morsels. Anything that's too tempting or too conveniently packaged. I have no problem with a growing, body-building 17 year old putting a packaged bar in his bag to tide him over on the go-- but if he comes home famished he should be making a sandwich, not eating three bars at once!
Previously certain (OK, all) family members too easily got into the habit of grabbing those kinds of things at all times. Surprisingly it didn't take very much adjustment (except for my youngest who took it on as a challenge to try to jimmy the lock--fortunately or not he's since moved on to older kid shenanigans).
I usually carry the key, and my husband and daughter know where one is tucked away. The boys have to ask.
If I need extra willpower for myself I leave my key upstairs. Even when I'm carrying it, it's amazing how that extra step of unlocking and needing to stoop down to look for/grab what you want makes you think twice!Best of all, I've noticed that when one of the cabinets is left open, the opportunistic feeding frenzies rarely happen anymore. I've retrained my kids to a more No-S attitude towards sweets!!
Cabinet locks are easily found in the big box hardware stores--littler hardware stores would have them too and locksmiths I'm sure as well. We installed them ourselves. The cabinet manufacturer offered magnet locks-- no good except for really young ones!
My tip would be if you are doing this and have multiple cabinets to put locks on--maybe in the garage or for cleaning supplies, consider buying locks with the same code. Each size/finish lock typically comes in a two or more key codes. Get the same one for all your locks then you can carry and use only one key for all the cabinets and have lots of spares. Some of the cabinet locks could even work on a drawer or free standing piece of furniture.
Hope this helps someone!