Hi, I haven't been on a good, consistent routine since Oct 2008. I was training very hard and consistently for about a year prior and built up some good strength and muscle definition. Since taking a 'break' from lifting I have gained fat and lost quite a bit of muscle and feel extremely soft and a little chubby

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I'm 5'8" and guesstimate weigh about 150lbs.
I plan on eating in a deficit to at least lose some chub for the summer.
So here's the question, while cutting, and considering my i probably don't have the greatest muscle base underneath, what is the best training routine?? I've already eliminated bodypart splits as a possibility and i'm torn between and upper/lower 4x per week or full body 3x per week.
I do lose weight pretty quickly and my only fear with dieting is looking skinny fat as I always have.
Any insight would be GREATLY appreciated!!