Hi my wife is 5 foot 1 and is obese although she exercises and eats well could it be thyroid or the citalopram possibly thanks?

Thoughts. The weight gain could be promoted by low thyroid function, but also could be a side effect from citalopram. Contact her doctor and get this fully evaluated.
Hard to say. but certainly both hypothyroidism (low thyroid) can result in weight gain, and most of the antidepressants, including celexa, (citalopram) are associated with weight gain. It usually, however, is related to taking in more energy (food) than one is putting out (activity/exercise). A dietician can review her diet and her health care provider can look into whether there are other factors, like thyroid problems.