Is Obesity the result of Malnutrition?

For some years now I have been researching data related to the decline in nutrient values in our food sources. For example the potato over the last 50 years has lost 100% of it's vitamin A content, 57% of it's vitamin C and 28% of it's calcium according to Canadian research! Bananas, tomatoes, peaches and most other vegetables and fruits tested show the same massive declines in nutrient levels. So our bodies can't get the same micro-nutrients with the same levels of consumption. We may have to eat twice as much food to get the minerals and vitamins our bodies crave! Guess what though ... in general the carbohydrate and fat levels in our foods have not declined! Therefore even those of us who don't eat junk food have to eat far more fat-making mass to get enough vitamins and minerals to metabolise it properly and to support good health.
Today, the only way to be slim, have healthy shining hair, good teeth and skin is to find another source of true-food nutrients, cut down on normal food sources, and exercise heaps!
Yes, I do believe that the obesity levels in developed nations is one of the results of mal-micro-nutrition.
But where can we find supplemental nutrients that are not synthetised from rocks and earth in a chemical factory?
I'll let you know when I find out!