I Have Had Colon Resection Surgery Several Months Ago. I

I have had colon resection surgery several months ago. I lost a lot of weight after the surgery. Now the weight just came on and I can't seem to get back to normal weight . I eat a well balanced diet , don't drink cokes, don't take sugar, do lots of juicing, drink smoothies , eat lot of salads. I don't under stand why unless it's got to do with the absorbition inside my body.