By Dr. Brian McDonough

By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – You want to keep the pounds off – get more exposure to natural light. That is the word from a Northwestern University study. Twenty minutes of natural light in the morning is associated with leaner figures.

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Researchers measured the light exposure of test subjects throughout the day with a wrist monitor. Exposure to bright light before noon was associated with lower body mass index even after controlling for other factors like diet, exercise and sleep.

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The researchers say get outside even on cloudy days.

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More research is needed before recommending natural light exposure as a helpful addition to weight-loss regimens. But in the case of getting outside and enjoying sunlight and fresh air, there are few arguments against it.