[noondip]

I believe you're meaning to allude to refined carbohydrates, like the ones found in soda drinks. "No carbs" would mean consuming no fruit or vegetables, at all - not exactly a practical strategy for healthful eating. (Note: grapes are especially high on the glycemic index and not an ideal representation of healthy carbohydrate, so your likening them to a can of soda isn't entirely inaccurate)

> The vegetarian diet (~60% of energy from carbohydrates,15% protein and 25% fat) consisted of vegetables, grains,legumes, fruits and nuts. Animal products were limited to amaximum of one portion of low-fat yogurt a day.

> In conclusion, a vegetarian diet led to a greater improve-ment in quality of life and mood. Patients consuming a vegetarian diet felt less constrained than those consuming the conventional diet. Disinhibition decreased with a vegetarian diet. The decrease in feelings of hunger tended to be greater in the vegetarian group. All these results suggest that a vegetarian diet is sustainable in the long term and may exhibit desired improvements not only in physical, but also in mental health of patients with Type 2 diabetes.

https://www.ncbi.nlm.nih.gov/pubmed/23050853