I am 5'6" and 176 pounds. I wear a size 16M in jeans and usually size 16 or XL tops. I'm 59 and wore a size 14 jeans in college when I weighed 135. But size 14 then was smaller than size 14 is today! About 10 years ago I was 156
and wore a size 14. But as already noted, sizes vary a lot from store to store and brand to brand.
5'10", 165 lbs, in maintenance now. Men's shirts are small, medium (mostly medium), or large, depending on the manufacturer. Jeans are 32" waist, but they are too large - I could use 31" or even 30" waist now.