During the two 'off' weeks, an ECA stack can be used as required. ECA will not cause such a pronounced down regulation and desensitization of the receptors, certainly not to the extent of clen. Ephedrine has a short half life in contrast to clen which results in times throughout the day where the betas will partially recover from stimulation by adrenaline and nor-adrenaline. Potency is also much weaker that that of clen, as it is not a specific agonist. Ephedrine is also thought to increase the conversion of endogenous/exogenous T4 to T3 through the activation of deiodinase enzymes responsible for this process. This is important as clen is known to slow the rate of T4 to T3 conversion. As a side note, some bodybuilders will use T3 concurrently with the Clenbuterol/ECA cutting cycle (together with certain anabolic/androgenic steroids no doubt!) in an attempt to at least maintain plasma T3 levels.
he might be confusing dieting athletes with non-dieting athletes. There's a difference between a glycogen-depleted run down athlete cutting to 5-6% bf vs someone in energy balance. Mike Young raised that possibility ( the energy deficit required to get than lean being the culprit, not bf% per se). I perform quite well at a low bodyfat%, but the last two weeks on my way to 5% bf were hard (I felt weaker and lost a rep here and there). Once I transitioned into maintenance, the feelings of weakness subsided and I regained strength.
Btw, I certainly don't agree with the notion that eating a paleo diet will automatically lead to 10% bf for men and 15% for women.