Excessive calorie decifit?

If I am understanding your question right, eating 1500 per day and burning 3000 calories would put you at -1500 calories a day.....so you wouldn't be getting any calories (fuel) for your body and you would be 1500 in the hole. I don't think a person could even survive very long doing that. My apologies if I did not understand the question.

i think you may be understanding the numbers given to you here wrong. the calories you burn a day that are used to determined what you should eat do not count as exercise calories

Yeah.. but they have enough fat that their bodies can live off of for a while. They also keep doctors on the set.. They are all very watched after.. I wouldn't recommend doing something like that unless you've got a personal trainer and a dietican on hand. My personal opinion.. But those guys do make me jealous.. losing 10 lbs in a week.. Where do I sign up!? :noway:

Theoretically, weight loss is a simple mathematical equation: calories out - calories in = calorie deficit. A 3500 calorie deficit = a weight loss of 1 pound. Most weight loss resources suggest aiming for a 500 calorie per day deficit so that you lose 1 pound each week (500 calories per day x 7 days = 3500 calories). The example I gave in my first post was merely hypothetical; I could have just as easily asked about a person eating 2000 calories per day and burning 3000 calories per day. The question is whether or not there is a point at which that deficit is great enough that it actually hinders fat loss, ie if you are taking in 1000 or 1500 or 97million calories fewer than you burn each day, do you actually impede fat loss?

Look at the people on the Biggest Loser. The trainers state that most of the participants are on 1200-1500 calorie per day diets, and their caloric output is targeted at 6000-8000 calories per day (which obviously sounds insane, but I'm just reporting what Bob said on the show); they seem to lose cartloads of weight every week. It seems like there would be a point at which the caloric deficit was so high that the body would stop functioning efficiently enough to continue to lose fat. Does anyone know if this is acutally the case?

The issue is not clear cut, due to the tremendous variation in individuals and how they respond. The general guidelines are that you shouldn't go above a 1000 Kcal/day deficit or below around 1,200 Kcal/day intake (this is the average person trying to lose weight on their own--a medically supervised program might be different).

The general sense from research I have read is that anyone on a restricted calorie diet (within the guidelines stated above) is going to lose some fat free mass (FFM) in addition to fat loss--some studies have reported up to 50% of total weight lost is FFM. The inclusion of exercise and strength training mitigated the loss of FFM compared to non-exercisers (in some cases by 50%), but they still lost FFM. From what I read, if you were going to go on a 2-3 lb/wk wt loss program, you are going to lose FFM, no matter what. It's a question that getting off the weight is more important short term than trying to conserve 100% of FFM. Reshaping your body composition comes a little farther down the road. That was certainly my experience when I lost 30 lbs in my first 2 months. Unfortunately, I did not take a thigh circumference when I started, but I noticed that my legs really decreased in size. I also really struggled to increase my weights when strength training. As I shifted to a less-aggressive calorie deficit, I started seeing steady increases and some notable increases in muscle mass (e.g. chest circumference).

The other research I saw suggested that resting metabolism also decreased with a reduced-calorie diet. This was also offset somewhat with exercise, but not completely. The interesting thing was that the change was not permanent--it reversed itself once subjects resumed a maintenance eating program. The study seemed to indicate that the concern of "permanent starvation mode" occurring as a byproduct of long-term very low calorie dieting was unfounded.

Again, these studies usually can only look at one small part of the big product, and it is a complex picture. So I would expect that others may have seen other research that may add some nuances or even suggest some different conclusions.

The way I look at it is that each individual has different needs, different goals, and different reasons for losing weight. For many people, there are several different stages to the process: Stage 1 is the need to see some fairly quick results, for both health reasons and as positive reinforcement. During this stage, losing some FFM or even slowing down metabolism a little is of secondary importance (but exercise is still crucial); Stage 2 is the "plateau" period, when results have slowed, but significant weight loss has occurred and now the person has the fitness level and the skills where they can ramp up their exercise program, be more aggressive with both cardio and strength and start reshaping your body; Stage 3 is the maintenance phase where the focus is on implementing behaviors that become part of a permanent lifestyle change and ensure that the weight loss is permanent.

It's not a fixed sequence--this is a general picture and I think many of us work on stages 2 and 3 simultaneously, but it is a general approach. Losing 10% of your body weight can have significant health benefits--much more significant than losing the last 10%. For those who are obese or have some acute health concerns, losing the initial weight fairly quickly is very significant--even if there are some negative side effects (i.e. loss of FFM). OTOH, 95% of "diets" fail within 2 years. Which is why one should be *extremely* wary of ANY short-term "success" claims. Personal anecdotes that trying a new supplement, or diet, or "cleanse" has resulted in significant weight loss in 2 wks or even 2 months time are useless in evaluating the effectiveness of the intervention.

One of the biggest criticisms of The Biggest Loser is that the weight loss results they show are unrealistic and set exaggerated and irresponsible expectations in the minds of viewers at home. I watched the show for the first time last week, and did some reading afterwards. From what I understand, despite the claim of "medical supervision", participants are free to engage in any extreme behavior they want to maximize their scale losses. In an interview, the first winner of TBL (can't remember his name) said that in the 2 weeks before his final weigh in, he ate almost no solid food, underwent numerous "cleanses", and finally resorted to the old-school wrestler practice of exercising in a rubber suit. He claimed that, by the end, he was so dehydrated he was urinating blood. He also stated that in the 2 weeks after the show ended he gained back almost 40 pounds as his body rehydrated itself and reestablished a more normal physiology. Other participants reported similar practices, although not to that extreme.