One of the biggest exercise myths is that you can lose fat in an area of the body by strength training or exercising that specific body part. The truth is that “spot reducing” and “spot reduction” does not work, because we cannot dictate from where our bodies will decide to oxidize fat, nor can we change fat into muscle. Doing triceps press-downs will not decrease the amount of fat clients have on the backs of their arms any more than doing crunches will decrease the amount of fat clients have on their stomachs.
As your clients age, their skin will become less elastic and thus conform less to their arms. So “flabby arms” are somewhat a product of age. Any exercise that decreases body fat percentage will help your clients lose fat on their arms, just as it will help them lose fat from other areas of the body. Source: http://www.ideafit.com/fitness-library/top-10-most-frequently-asked-questions-in-a-fitness-center-and-their-answers