Before I start I need to add a bit of a proviso – this is a personal philosophy, not completely backed up by current research that I can find. While I do have research to support my hypothesis, that is all it is, a hypothesis. So take it as you will.

The health industry proposing that a two pounds a week weight loss regiment as being ideal is wrong for people whose BMI is above 35 (mine is 45 at the moment).

Without meaning to be crass, people with a BMI above 35 shit more than two pounds in a day. The variance that obese people experience is upwards of 5 lbs in the course of a week just through maintenance alone.  

Let’s put this into perspective. When the health industry talks about two pounds per week they are really talking about people who are in either the normal or marginally overweight category. More specifically, women for whom the stereotype of having the perfect physique is plastered over every website, newspaper, and cable channel for the last 50 years.

Even websites like calorieking.com, base their exercise to burn off a portion of food are based on a 35 year old female who is 5’7″ and weighs 144 lbs (BMI approx 22.5). 

That same woman, with a BMI of 27 (overweight) and who is approximately 175 lbs, 2 pounds per week equates to 1.15% per week. This is doable and is motivational because (and yes I’m ignoring a woman’s natural weight gain and loss due to her cycle period) the amount of weight variation is far less the less you weigh. 

Now – take that same percentage and apply it to someone with a BMI of 45 and is 320. The average weight loss should be 3.7 lbs per week based on a similar ratio. 

Let’s assume for a moment that a normal, healthy diet is 2500 calories per day. That is 17500 calories per week.

However, 3.7 lbs weight loss to achieve the same 1.15% drop per week is 13320 calories.

That means in order to drop a comparable amount of weight, you would be restricted to roughly 600 calories per day in order to achieve the same motivation.

Here is the kicker thou. When you reduce your calorie intake the body naturally wants to conserve its stores of energy. Your metabolism drops to adjust to the new calorie intake and typically doesn’t go back up to where it was previously [1]. 

It seems however that more and more research is coming out in support of fasting as it doesn’t have the same impact on a person’s resting metabolism as when being on a reduced calorie diet [2] [3] [4].

There is no specific research I have found currently that indicates what is the lower limit that can be considered ‘fasting’. Several pop culture references seem to place the lower limit in around the 300 calories per day range [5]. Another study which was based on a 1/3rd reduction in calories for 2 weeks followed by 2 weeks of eating normally also seems to indicate that metabolism can be maintained while reducing weight [6].

It would appear that two main factors are at play here.

One, that metabolism responds negatively to prolonged calorie deficiencies that extend beyond two weeks in length. 

Two, that metabolism responds positively to calorie deficiencies that are at least 3-4 days in length as compared to typical intermediate fasting regimes [7]. Further, that these types of intermediate fasting regimes, on the surface, are no more effective than standard very low calorie deficit diets [8].

It would seem to me that short term intermediate fasts at least 5 days in length with no more than 300 calories per day, broken with periods of regular calorie intake, may be the most appropriate method of reducing weight and maintaining metabolism longer term. It provides immediate benefits in terms of weight loss that is visible, it helps to maintain ones metabolism, and can be maintained longer term as it is not as restrictive as going completely off food altogether.

As there is no complimentary study that talks about whether the ratio between fasting and eating should be 50/50 or not in order to maintain metabolism function, this is still wide open country in terms of what may work or not work.

Regardless, the concept that ‘two pounds per week’ is healthy is looking less and less likely. While it may help people in lower BMI weight categories, the prolonged calorie deficit seems to be more harmful in the long run than doing intermittent fasts which may provide more benefit to metabolism. At the very least the evidence over the past ten years seems clear that prolonged calorie deficiency is a life long change for the worse, not the better.

While the immediate health implications of a lower BMI are certainly important, and in some cases of more consequence than the negative implications of having a slower metabolism, there is also no clear cut evidence that the reverse is true either. Since a lower metabolism is a given with calorie reduction as compared to fasting, and each share equal success in lowering BMI, I would think that fasting should be the preferred method of weight reduction having potentially fewer side effects than calorie reduction.

The outstanding questions in my mind however are still a) how many calories are considered fasting, b) how long to fast (in days, not hours), and c) what is the appropriate interval between fasting periods.

I have some hypotheses which will be discussed and tested later.

— Kevin