Elizabeth weighs 164 pounds, and when she exercises she loses 500 calories. How many pounds will she weigh in one month?
One pound of body weight is equal to 3500 calories. Therefore, losing 500 calories per exercise session will result in a weight loss of 500/3500 = <<500/3500=0.14285714285714285>>0.143 pounds.
A month typically contains 30 days, so in one month, Elizabeth will lose 30 * 0.143 = <<30*0.143=4.29>>4.29 pounds.
Therefore, Elizabeth will weigh 164 - 4.29 = <<164-4.29=159.71>>159.71 pounds in one month. Answer: \boxed{159.71}.