Female Weight Gain with Workouts

Question:

I have a client in her late 20s. She has been slightly underweight for some time, but is very athletic and lean. She came to me with the desire to increase her overall functional/core strength and to correct her many biomechanical imbalances of the kinetic chain. She did not desire to gain any more weight, but it certainly would not hurt her!

She has made great gains in the desired areas in our work together. However, in a month, she has gained about 10 pounds, mostly muscle and some fat, but she claims is eating no differently, less if anything and exercising more cardio-wise. She is not happy about this unexplainable weight gain. It is my feeling that this weight gain is beneficial for her, since she looks and feels healthier. However, it seems odd that for years she has been the same weight, and all of a sudden this has changed. I suspect it is because she is doing more cardio, eating less and slacking off on her resistance training, and therefore, her metabolism has slowed.

I explained this to her, advising her to cut back on her cardio to 6 hours a week as opposed to 10, increase her resistance training frequency and increase her caloric intake by about 500 a day. I also advised her to maintain her weight because she was slightly too thin prior to the weight gain. Could she have slowed her metabolism enough to contribute to this sudden weight gain? Will she be able to speed up her metabolism by the regimen I have suggested? Any suggestions or insights you have will be much appreciated!

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