There is a way to review the food supply for the amounts of food by type that we consume each year.  This is done with surveillance data from the USDA.  It is called US  Food Supply Data.  Researchers do a good job estimating what actually ends up in our homes.  For example, they account for parts that are not edible and what might get lost along the way (spoilage/waste). Of course, they can not be certain of how much we eat or toss out within our own homes.

I am reading an article now that was published in Food Review in 2000.  Unfortunately, it is comparing our estimated intakes to the recommendations of an older set of Dietary Guidelines.  In the article there is data from 1970 thru 1999.  It compares a few sets of years, but I am most interested in the changes between 1970 and 1999 when the obesity epidemic took off.

Here are a few highlights from the article.

We have reduced some of our full fat milk consumption but increased cheese consumption which is high in saturated fat.
The vegetables we were eating in 1999 were far from ideal. If you consider the AHEI - it is horrible.  Fifty two percent of vegetable consumption involved five foods and three of them were potatoes.  The same bad news for fruits.  The main fruits consumed were bananas and orange JUICE - not oranges.

Based on the old guidelines, we were to aim for no more than 30% of our calories from total fat.  That has changed to a recommendation to limit saturated fats and increase healthy ones.  The newest guidelines recommend strict limitation of solid fats and added sugars, SoFAS. From 1970 to 1999 we increased our consumption of added fats by 32% (or 64 grams) but what's worse is that it makes up 87% of the total.  This leaves very little room for the fats that occur naturally in meats.  (the added ones are from  baked goods, dairy creamers, butter and salad dressings).  We have increased our added sugar consumption by 29% .  This comes from desserts (refined grains) and sodas.  In fact, the average person (if things were really evened out) consumed 34 tsp of sugar a day in 1999.  That is almost 4 cans of soda!
I was particularly interested in the meat, poultry and fish section - considering the recent posts on a healthy eating index.  In 1999, we were consuming three 4 oz servings of red meat a day.  Recall that the ten point score was for less than one red meat serving a month!  Also, that is an underestimate because they are averaging it across all of us, including vegetarians who consume 0 red meat.

This type of study does not allow for causal conclusions, however - with what we know about diet and disease it certainly shows that our increase in added fats, sugars, refined carbs (and the 15% increase in overall calories) matches our rise in obesity, heart disease and diabetes.  In 1970, 46% of adults were overweight or obese and now it is about 67%.  In 1970, 15% were obese and now that is over 30%.  
We did not change the foods we eat near as much as the foods we ate CHANGED.  It is time to alter our food supply back to the way it used to be.  We can get rid of all this extra fat and sugar that most of us have no idea is even there.  A person shouldn't need a college degree to navigate the food environment!

Putnam, J., Kantor, L. S., & Allshouse, J. (2000). Per capita food supply trends: progress toward dietary guidelines. Food review, 23(3), 2-14.