These are all classifications based upon the manner of reproduction of the plant. They are all under the main classification of "Vegetable." Vegetable includes all vegetation too, including fruits, trees, non-edible plants, grass etc. Fruit is simply an external ovum-- Fruit is technically a seed too, but it has a protective fleshy covering. The reason it is sweet is to attract birds and animals to eat the seed to spread it through defecation. Vegetables like beans and tomatos are actually fruit because they are the external ovum of vegetables.Originally Posted by redbeans
I'm assuming you mean fruits and such not grains or legumes or nuts. Winter squash are high in sugars and starches and some protein. So-called "white" potatoes are very starchy and are moderately good sources of protein especially if combined with legumes. Many root crops like carrots and beets contain sugars. I just don't know if you could eat enough carrots in day to supply your calorie needs.
Nuts, soy beans, peanuts (technically these are not fruits or vegetabels but seeds) are rich in calories but may be too high in fats and oils to be recommended as a primary calorie source. Use in moderation.
Apologies for getting pedantic (can't help myself sometimes).