Athlete Tries A FAT DAD BOD For 48 Hours - Mark Lewis

Aug 13, 2025

Intro This is a quick summary of Athlete Tries A FAT DAD BOD For 48 Hours from Mark Lewis. It’s a fun, eye‑opening experiment — we’re breaking it down so you can try the workout today. Be sure to check out the full video for all the details.

Key Points

Adding 8‑10 kg (≈ 18‑22 lb) of body‑fat dramatically slows speed (track 400 m laps go from ~1:05–1:06 to >1:10) and makes temperature regulation harder.
The body’s “bouncing” and extra weight feel like a rock sack; you’ll need a baggy shirt and extra hydration.
Mental resilience matters: the “dad‑bod” still lets you run a 5 km in ~22 min, but it feels much harder.
Practical tip: use a longer‑rest interval workout to gauge how weight affects pace, then adjust your regular training.

Workout Example Track Interval (400 m repeats) Intervals are a fantastic way to measure changes in performance. For a deeper look at how to structure these sessions, you can explore our guide on Mastering Interval Training: Science-Backed Workouts and How a Smart App Can Personalize Them.

Warm‑up 10‑15 min easy jog.
4 × 400 m at a target pace of 1:05‑1:06 per lap (the pace you can hold when you’re at peak fitness).
Rest 2‑3 min between repeats (walk or light jog).
If you stay under 1:10 per lap, add a 5th repeat.

5 km Run (post‑weight‑gain)

Run 5 km at a comfortable, steady pace (Mark’s 5 km took ~22 min with the extra weight).
Focus on steady breathing, and note that the extra mass makes the run feel ~30‑40 % harder.
While this experiment is about slowing down, once you’re ready to speed back up, check out our guide on Mastering 5K Speed: Proven Interval Strategies to Cut Minutes off Your Time.

Zwift Hill (Optional)

Set your weight in Zwift to 104 kg (the weight he reached).
Choose a long hill (≈20 min) and ride at a steady effort; expect a 20‑30 % slower cadence than usual.
Keep fluids, electrolytes, and a good cooling strategy (fans, open windows) because you’ll overheat quickly.

Closing Note Give this “dad‑bod” test a go—adjust the lap paces and 5 km time to match your own weight and fitness level. Use the Pacing app to customise the intervals for your current paces, and see how your body responds. This is a great way to appreciate how your body performs at its peak. Once you’re ready to tackle new goals, whether it’s a faster 5k or stepping up to a new challenge, you’ll have a fresh perspective. For those looking to go further, our guide to Mastering the 10K: Proven Training Plans, Pace Strategies, and How a Smart App Can Elevate Your Performance can help you prepare for the next distance.

Have fun, stay safe, and enjoy the challenge! 🚀