Are you kidding? This is terrible advise. A heart attack does not count as fat burning ability.
My encyclopedia-esque Saved By The Bell knowledge aside, it is not terrible advice. Allow me to provide a more calm response.
Caffeine has proven, throughout the years, to be one of the most effective and safe stimulants. Especially since the fitness boom of the 1980s, there have been lots of scientific studies on fat-burners...specifically, which ones are the most effective yet safe. The two that work the best and have the least side-effects are caffeine and ephedra, both natural supplements found in various plants. Ephedra got a bad rap and in a knee-jerk reaction was banned for sale in the U.S. Most other countries still allow Ephedra. The only way that Ephedra is even remotely deadly is in extremely massive quantities.
Caffeine is not deadly at all. While it is true that the body builds up a tolerance for it, it is next to impossible to "overdose" on caffeine. It is mildly addictive, however (just look at your parents...my dad drink a pot of coffee in the morning...just so he can go walk the quarter mile to the coffee shop and get a coffee.) But it also has no adverse physical withdrawal symptoms. You will crave it, and will feel pretty tired when quitting caffeine, but all in all it is a fairly harmless addiction.
Now, as a bodybuilder and weightlifter, I've used all manner of caffeine supplements over the years. The new prevailing wisdom amongst the fitness community is that the best caffeine supplement pre-workout is a cup of black coffee or green tea. It's enough to helpfully elevate your heart rate without getting you jittery like a solid dose of pure caffeine will.
To say that coffee or a No-Doz pill will give you a heart attack doing any physical activity, much less one as mild as disc golf, is a frankly hysterical reaction. If you are so obese or out-of-shape that disc golf in any form will give you a heart attack, then you should probably see your physician for some alternate weight-loss methods. Disc Golf is a supremely low-impact activity, especially on smaller public courses that don't require 500-foot drives. My 58 year-old father with no right achilles tendon, two shot out knees, a gimpy back and an aching hip and shoulder still plays 3-5 rounds per week in addition to his physical therapy and his gym time. His physician even recommended playing more if his schedule allows.
So the addition of caffeine to a round is really a non-factor. It will bump you heart rate up a few beats per minute and help get you into a higher zone for fat burning. it WILL NOT give you a heart attack. Fact.
Last thing: I am a huge proponent and supporter of DDP Yoga. I do one or two sessions every day. Today, I did the "Wake Up" session, went and played a round, and then did the "Fat Burner" session...and I'm feeling great. For all of us older guys on here, do yourself a favor and get into yoga (preferably DDP Yoga which focuses on dynamic resistance to help you burn calories while stretching your body) and thank me later.