That depends on whether you are actually getting fatter or just mean you are getting bloated.
I am a small build and a size 8 (australian) normally. My stomach is flat and I fit into all my clothes. One can of Jim Beam, some Sugar or some bread can cause me to increase my stomach area and side area within about 5 minutes, so much that I only fit into size 10-12 clothes and hardly any of my other clothes even fit. Then I do a Bowel Cleanse or diet properly for a day and back down again.
Is this what you mean. If so you may be eating foods you are allergic to or eating something that you shouldnt in terms of candida. Make sure you are doing candida diet properly and taking antifungals and priobiotics and see what happens.