Hugh,
In response to the low calorie diet, I would like to put my wife’s experience as an example. She is allergic to wheat and as such has converted to a paleo diet. Google “paleo” if you have wheat issues. In her case when going off the high sugar, starch, and carb diets she experienced the weak and low energy days too. However, as her body adapted to it in about 3 or four days she felt normal. Your body will adjust and “retool” to the new foods as well as the lower calorie intake. You may not have stayed with it long enough. I know it’s easier to write it than actually do it.
Of course the benefits for her were of a different issue not a weight issue. So dropping to a lower calorie diet may feel lethargic for a bit, but you will adjust when the time comes or get on it at a slower pace, drop 500 calories a week to get there. If it helps just consider the spare tire (in my case) as just my “on board” GOOD bag worth about an extra day of calories. America’s six pack mentality isn’t the only “healthy” out there. Stay healthy and active. S.P.