like most in here have suggested
1. take 1-2 showers with soap (1 in the morning and 1 in the evening, if you only have time for one shower, then take it during the evening)
2. stick to a good diet. drink lots of water to flush out the system and to get hydrated ..exercise as well. eat veggies, increase fiber intake instead of other carbs.
3. try not to touch your acnes as you'll get the pores more dirty and might inflame them, let your body cope with them naturally.
4. put some lotion on your body (that has vitamin E)
i had/have a similar problem. gained a whoppin 50lbs in a few months or so, and i got a handful of "bumps" on my body. 1 on each upper arms and 2 on my chest and one on my back. at first i thought it was just a regular pimple and it would go away, totally forgot about them but after 2 years or so they would still be there! finally went to the doctor, he gave me some antibiotics, took it and it kinda helped, but he told me to shower more and such stuff. eventually one or two of them started to vanish (still there but much much smaller now). anyways it's been a year now and i just started to realize i haven't done much to get rid of these acnes. i shedded a lot of lbs in the past couple of months, about 35lbs, but it didnt help since i dont eat right. anyways, the past couple of days i've applied those generic cleansing for acnes - they're suppose to be facial cleansers, but i apply them on my arm and chest and i use dove soap religiously when taking a shower, and i've noticed a difference. so that's my 2 cents for ya