100 years ago was not the Middle Ages, that ended about 500 years ago. 100 years ago is the late modern period.

I think I replied to the wrong comment. My mistake.

Why? There is evidence suggesting that the number calories available and the general quality of nutrition for median person increased after the collapse of the Roman empire.

Both because of a significant decrease in taxation but mostly because the plague, climate change and warfare killed half or so killed half of the people living in Europe at the time.

The same thing happened in the 1300s and 1400s as the number of people decreases significantly the quality of life for those who remained increased (more land per capita).

Additionally there were significant technological developments during the middle ages which resulted in higher crop yields (especially in northern Europe) (heavy plow, horse collars, wind mills, more water mills, 3 and later 4 field crop rotation, general improvements in metallurgy...