Couple of stories!
Our company had a health fair expo type thingy. One of the tables was set up as a BMI exhibit. I had my BMI measured with a hand held type unit. It read at 30%. The rep said I should seek medical attention cause I was borderline obese. I'm now 245, back then 220 and training with major climbs. The guy behind me giggled as he measured at 10 %. He knew I was a roadie and part time MTB'er. He was an MTB'er. There was a group of about 5 guys that were serious riders according to themselves. The guy asked if I wanted to mtb with hiom someday. Sure, I met him at the bootm of the mtn. He had a lightweight MTB. Went so far as having the paint stripped for weight savings. Was a nice lite rig. I had a stock Trek 8000.
The course was a 5 mile loop. 2 1/2 serious climb, then down. We started off then within 1 mile, he was out of sight....behind me!
I waited at the top for about 10 minutes. My best was 26 minutes on the climb. He showed up and wa shocked. He said he had a bad day so we'd go back next week. No problem. I did the loop 3 times ,2 or 3 times a week. Most riders are happy to complete one loop. Hard core racers will do 2 or 3 loops.
We went back the next week. He said before the ride not to wait for him cause he wouldn't wait for me. No problem. I completed the loop and waited about 20 minutes for him! None of the other riders wanted to ride with me after that!
Second story, after I had gained about 5 pounds, I figured I was still in good shape at 225. Famil;y still said I ws too skinny. I did a ride in San Diego, the Alpine Challenge. 6500 ft in 72 miles. Easy compared to a none of the rides I had done several times.
I ran into aguy that looks like the guy in the OP. SHort raound looking guy. I was pulling up onhim in the hills. I thought to myself," I got this guy fo sho!" after passing one of the guys I used as a rabbit in training rides. I knew I was having a good day.
The guy saw me coming up and put the pedal to the metal. He started to pull away and all I could do was watch. I thought for sure he was a sitting duck but he sure tore me a new one!
But the first time was by a woman about the same build as the guy in the picture. It was a 7% one mile climb on the Rosarito/Mexico ride. She dropped me like a hot potato! That's when I learned not to underestimate anyone!