I tallied up my last 39 days or so of experiences on a South Beach-similar approach and then a calorie-limited Kwasniewski approach.
Here's what I ended up with:
Weight loss on the South Beach-similar approach: Over 1 month, lost 4.6 lbs. (could be more like 3 if I ignore the upward fluctuation above norm that preceded the first day).
Weight loss on calorie-limited Kwasniewski: Over 9 days, lost additional 4.6 lbs.
(Could some be water weight as is found when you lower carbs? Yes, although in the past when I've gone from something like 20 carbs a day to more like 60 I haven't noticed significant upward weight fluctuation in the next several days. My body fat percentages have stayed about the same throughout the last 39 days.)
Here's more detail:
South Beach-like approach over 30 days - mainly phase 1, a little phase 2 (may be higher fat than other South Beachers would have):
Weight loss: 4.6 lbs.
Typical average daily intakes over a week:
Calories: 1,228
Fat: 39.3g
Carb: 80.1g
Protein: 135.9g
Burned through exercise: 47 calories
(About 45% of calories are from protein, 29% fat and 26% carb.)
High-fat, limited protein, carb, calorie Kwasniewski approach for 9 days:
Weight loss: 4.6 lbs.
Average daily intakes over the last week:
Calories: 1,277
Fat: 95g (52g saturated)
Carb: 36g
Protein: 64g
Burned through exercise: 36 calories
(About 68% of calories are from fat, 20% from protein and 12% from carb.)
I should add that, for me, this is all unusual progress. My history for much of my life is not losing, and sometimes gaining, on these kind of calorie intakes. For me, the South Beach approach is lower fat and higher protein than I would normally tend to, and the Kwasniewski approach is much higher fat than I would normally tend to.
I've felt pretty good on both plans. I have had more energy since starting the Kwasniewski-esque plan and it is, in a very pronounced way, like when I breathe I'm getting a deeper breath or I'm in the middle of a woods or countryside area with terrific fresh air... though I never felt anything that I would describe as a breathing problem before at any weight. But I did do an exercise test once a few years ago (while on a relatively low carb and calorie-limited plan, as has been typical) and came up with slightly lowish
Vo2 max though. That's low maximum oxygen uptake, a measure of aerobic capacity. When you don't have high VO2 max, as I understand it, you don't exactly feel like doing sprints - when you exercise, lower-level endurance exercise is easier and more feasible.