Is it enough? maybe not all by itself, but it will certainly help, along with cleaning up your diet. If you could do something every day for exercise it would be even better.

Starting with what you can do and increasing time and/or intensity of exercise as you become more fit (rather than going out and trying to be a super athlete immediately) seems to be a good tactic. For inspiration, check out Laurie Ann March's story here (she's the author of a couple of excellent backpacking cookbooks). Over time she has reduced her weight quite dramatically, starting with just walking and eating wisely.
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dk