I wanted to update my comment that it is indeed possible (not necessarily easy) to safely lose a large amount weight in a short time but as I said it is also a short-term solution that cannot be maintained but can be used as a sort of shock to the system.
Please note I did not mention calorie reduction as a means to lose the weight as that is not a feasible way to lose above the 1 pound a week recommendation the reason is simple math (although body chemistry is not simple math and varies all the time hence the reason the quick weight loss will only work for a short time).
Using pure math assuming your body does not lower your basal metabolic rate (the amount of energy/calories your body converts daily just to exist) which it will on extreme calorie reduction, to lose 7 pounds in 7 days you would need to remove about 3500 calories a day from your diet. I would assume this is not possible as you are consuming less than that many calories a day so even if you didn't eat for a week you wouldn't lose a pound a day (since most people consume between 1500-2500 calories daily).
The more important to note dangerous part of this method of weight loss (notice I said weight not fat as this causes weight loss from many sources in your body) is if you do a massive calorie reduction you may start losing weight but your body will think it is starving to death (which it is), so it will reduce your basal metabolic rate as much as possible (the opposite of what you want) and it will need to look for other sources of energy to maintain body functions (since your are not supplying enough through eating) so it will start burning fat stores but fat to energy (calorie) conversion is a slower process so to compensate for the massive calorie reduction and fluctuating calorie burn as you go through your day, it will also start breaking down your bodies components for energy production usually muscle first which has a faster conversion rate (please note that muscle is an active tissue that just by existing burns calories so again the opposite of what you want long term and is not the kind of weight you wish to lose as muscle weight loss gives you that super skinny/anorexic unhealthy look).
This starvation completely sends the body systems out of whack and causes many unhealthy side effects as various body systems are compromised for calorie sources and/or these systems are interrupted or not operating normally to save energy (i.e. health concerns/sickness).
Alternatively what I was recommending was keeping your saturatedfat intake low (but still get good unsaturated and poly-unsaturated fats) increasing your protein intake which will in turn lower your carb intake (I assume you are watching your total calorie intake) and doing a H.I.T. (High Intensity Training) program like the high rep weight training I mentioned. Doing this it is possible to temporarily shock the system and increase your basal metabolic rate by 1000-2000 calories a day (which is a 24 hour controlled burn rate which fat stores can normally handle as the main energy source) that in addition to the actual calorie burn of the H.I.T. training (in my case about 1000 calories a workout) makes it possible to lose large amounts of fat in a short period while maintaining most muscle mass (body building circles call it cutting, reducing body fat while maintaning muscle mass).
But as I said earlier this is only a short term solution for many many reasons two of which are your body will adjust and get used to the new training method and will most likely dial back the basal metabolic burn rate somewhat and doing this kind of intense training is very draining on ATP and glycogen stores in the muscles. I find for me after about two weeks my training loses its effectiveness as I can't keep the intensity the training needs to be effective i.e. I went for three weeks on this H.I.T. cycle and only lost 1/2 pound this last week as opposed to the 8.5 pounds total during the first two weeks. Also i found my intensity levels during training are down (running out of energy sooner) so I am moving back to a power/hypertrophy method of weight training now and giving the H.I.T. program a rest for a while.
I may work this in for another 2 week cycle in 2-3 months once my body fully replenishes itself to see if I can generate another short term quick loss.
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