10 lbs of fat is 36,000 calories. Which is:
- 82 miles of swimming
- 240 miles of running
- 700 to 900 miles of biking
26 lbs obviously being 2.6 times that: 200+ miles swimming, 600 miles of running, 2400 miles of biking.
So as you point out, 26 lbs lost isn't going to happen even if he ran that 1 mile every day for 3 months. The ONLY way is substantial caloric deficit through dieting/reduced food intake.
Fun fact: If you stop eating completely, your metabolism goes down.
Still, with a basal metabolism of 1500 calories (daily) and no food, you would lose 160g of fat (daily). You can add exercise to lose more fat, and keep your muscle.
You could also stop eating (only water allowed) for 74 days and lose around 10 pounds (combined fat and muscle)
This is the reason diets don't work longterm. It takes great willpower (which the person didn't have much of to begin with) for a really long time (probably for life)
You can lose 10 pounds in 35 days by just eating at a healthy calorie deficit.