HAH! FOUND IT! Per the IRS guidelines:
You can include in medical expenses amounts you pay to lose weight if it is a treatment for a specific disease diagnosed by a physician (such as obesity, hypertension, or heart disease). This includes fees you pay for membership in a weight reduction group as well as fees for attendance at periodic meetings. You cannot include membership dues in a gym, health club, or spa as medical expenses, but you can include separate fees charged there for weight loss activities.
You cannot include the cost of diet food or beverages in medical expenses because the diet food and beverages substitute for what is normally consumed to satisfy nutritional needs. You can include the cost of special food in medical expenses only if:
1.The food does not satisfy normal nutritional needs,
2.The food alleviates or treats an illness, and
3.The need for the food is substantiated by a physician.
The amount you can include in medical expenses is limited to the amount by which the cost of the special food exceeds the cost of a normal diet. See also Weight-Loss Program under What Expenses Are Not Includible, later.