Some more personal musings on why I think in this society as a whole here in the western world we generally struggle with too much weight, from a scientific-ish perspective.
I was parusing the Kapha diet list, as I often do, and noticed something in common with the foods Kaphas should avoid:
Vegetables ~ cucumber, olives, sweet potatoes, squash, tomatoes, zucchini
Fruits ~ bananas, dates, figs, melons, oranges, plums, watermelon
Legumes ~ soy products
Dairy ~ almost all dairy
Grains ~ yeasted bread, oats, pasta, rice, wheat
Nuts & Seeds ~ all nuts, peanuts, halva, sesame, tahini
If I think to cultures that historically have struggled with providing enough calories or tissue-building sustenance, including Europeans, Asians, Middle Easterns, North Africans, their food staples tend to be those of the list above, which promote weight gain! These cultures also love deep frying, a sure-fire way to hold on to kapha tissues like fat in our bodies.
As well, I think maybe on a genetic level, humans (like most animals -- think of your overweight house cat) are built to absorb these Kapha-heavy calories efficiently and hang on to them dearly, in case of famine, cold weather, et cetera. Maybe the ease with which we adopt a sedentary lifestyle supports this body drive. This is why I think it's so hard for us to resist our cravings for things like fried foods, sweets, breads, and carbohydrates -- emotional stuff aside. The most popular fast foods and restaurant chains after all are based on these Kapha foods -- pizza, subs, fries, burgers, pasta, chocolate bars, chips, and so on.
Interestingly, the foods that are most Kapha-friendly (so, foods that don't promote weight gain) are South American in origin:
Corn, quinoa, white potatoes, ancient grains, plantains, all beans, limes, grapes, cilantro, chilis, onions, garlic...
It would be interesting to take a comparative look at cultures around the world that haven't been affected by globalization and modern trends and see what the diet is and respective health and fitness of the population.
Now that many of us (likely anyone with the means to have internet access to be able to read this post) have an enormous choice in what we eat, how warmly we're protected from the cold, and how much activity we have on a daily basis, we can choose to eat in a way that truly supports our individual dosha, rather than generally as a population put on as much weight as our agriculture will allow and our genes are programmed to do. We can be conscious of our cravings and physical desires (or lack thereof) and decide compassionately what we give in to and what we challenge for the sake of our health and happiness. And with this great personal power comes great responsibility! Or rather, it's always harder to choose against our perhaps-genetic desires when they're simply a generation or two behind today's reality.
Hope this has been an interesting insight! : )