Good news, 30 minutes of exercise each day is better than one hour. On average, men who exercised 30 minutes a day lost ~8 lbs in three months, while those who exercised for a whole hour only lost ~6 lbs. One explanation is that half an hour of exercise is so doable that study participants had the desire and energy for more physical activity after their daily exercise session. Those who exercised for 60 minutes per day probably ate more, thus their weight loss was slightly less than anticipated.
American Journal of Physiology, September 2012