I've seen exactly the opposite of this -- that when a person eliminates refined sugar and/or carbs, they are able to treat diabetes without medication.
Also, those who refrain from sugar/carbs lose a lot of weight. It seems to be a proven healthy way to eat.
It's also a fact that refined sugar and carbs in everything hasn't been possible before the Modern Age, with high-speed transport, agri-business, factories producing most of our food, etc.
Unless you lived somewhere that grew sugar cane (note: this is only a minority of places!) the only source of "sweet stuff" would be honey and fruit. And fruit only grew for X months of the year -- sure, they made preserves for the winter, but you couldn't eat it like it was going out of style, or you'd run out. Ditto for honey. Bees can only produce so much honey per year.
Today, they put High Fructose Corn Syrup in everything. Just read the labels! Also, most processed food contains extra carbs in the form of soy "fillers", flours, and what not.
Don't pump added refined sugar or HFCS with a carb based diet. Grains have been the main food in most cultures since the plow was invented. Whatever grain or starchy vegetable could grow in that climate became a staple. The high carb- no meat - low fat diet to improve health is not soda and candy. It's based on minimally processed starchy vegetables, whole grains, and legumes, with fruit and non starchy vegetables added.