[001sky]

I upped my exercise, cycling 30-40 miles a day, every day for the first couple of weeks.

Good to see!! When you are burning this level of level of energy every day, its actually <hard> to keep a stable weight. (Author must have had some base fitness, too so good for him.)

At its core, Weight change is simple input/output math. The key variable is %deplete your glycogen levels (as % of full everyday.) That is the "cache" of energy from your daily diet. If you burn enough energy to deplete this, you will lose weight, as your body replenishes itself from non-dietary reserves (fat, protein en extremis).

Surprisingsly, these are highly realistic numbers (<1lb/day>), even for relatively fit (height/weight proportionate) people. Moderating the pace to emphasise endurance over power will lead to more loss of net-mass. Asympotically, you will reach a point of gradual returns, but it is not at all surprising to lose significant mass under such prolonged workloads.

TLDR: Glad to see this is not a crash diet.

edits: clarity

[ironchef]

"At its core, Weight change is simple input/output math." But I also think that...at its core it's very complex. What if you do all of that input in a single large meal vs 6 smaller meals? That's a BIG difference. Similarly just doing lots of cardio (and "burning" calories) vs high intensity workouts (like crossfit) have very different results.

[001sky]

If you're interested in simplifying the analsis, don't look at people who are trying to lose weight for your data. Look at people who are fighting to keep it on!! Read up on people who have to do significant amounts of work under limited caloric availability (not caloric restriction per se). At that level, 6 smaller meals keeps weight on (more efficient digestion). Eating fat leads to more weight loss (heat entropy). At a certain stage, how you do the work (cardio/crossfit) etc is irrelevant, because the order of magnitude of output=input. For a normal person at a gym, they are at a fraction of this workload. Walking an 4m/hour a day burns 400 calories a day. That's an order of magnitude off your metabolic rate of 2500/day. Walk or run 10 hours a day, you will burn 4000-8000 calories a day. You will deplete glycogen at hour 3-4 without a couple of those six meals. If you do this for 60 days on a 2500 calorie diet, even if its 40% fat, you will lose weight. Probably pushing yourself into unhealthy territory afer only a fraction of that time (if you have a standard BMI). That's a non-cardio, non-intensive workout BTW. That stuff is irrelevant, provided your metabolism is set to max by dynamic caloric consumption requirements at the same order of magnitude as base metabolic reuquirements. Cycling 40 miles a day (as the author claimed) is much closer to this threshold than other examples.