In Ayurveda, diabetes is broadly understood as "Prameha".

.Dietary Causes 

Excess intake of:

Sweet foods (Madhura rasa)

Heavy, oily, cold foods

Dairy excess (curd, milk products)

Freshly harvested grains, jaggery

Frequent eating without the digestion of previous meal .

Lifestyle Causes 

Sedentary lifestyle (lack of exercise)

Excess sleep, especially day sleep.

Lack of physical activity

Comfort-seeking habits (no exertion)

Dietary Prevention

Reduce:

Excess sugar, refined food.

Heavy, oily, fried foods

Prefer:

Barley (Yava), millets, and old rice (atleast 6-8 months old.)

Bitter foods (Neem, Karela) in curry.

High-fiber diet

Follow timely eating and avoid overeating.