Calorie intake vs. calorie expenditure

Ever since I can remember I have been struggling with my weight (understatement of the year).  I have read many books on the subject and I even got a PhD in Biochemistry.  I have read thousands of journal articles but here I am, fat yet again.  You see, I don't have a big problem with losing weight but I struggle to keep it off.  For me the recipe for weight loss has always been simple.  Eat less calories than what I expend (read: starve myself) and exercise to increase my calorie expenditure (read: 45 minute jogs every single day).

No wonder the following graph (linked from http://www.hussmanfitness.org which is a good source of information on fitness and diet) has, for so many years, been an extremely valuable reference point in my arsenal of information on weight loss.  This is also why I decided to include it in the first post of this blog.

You can see from this graph that losing weight is actually quite simple.  John Hussman shows without a doubt that your cumulative fat loss will follow the same trend as your caloric deficit does.  The reason he divides his cumulative caloric deficit by 3500 is because it takes about 3500 calories to lose one pound of fat (one pound = 450 grams.  There's about 8 calories in every gram of fat.  Thus, 450 * 8 = 3600 calories).  This all makes sense, this is basic thermodynamics, right?

However, I occasionally stumble upon articles such as those from Richard Feinman the biochemist (not Richard Feynman the physicist) who is credited for doing the first serious research on the Atkins diet.  His work states that a calorie is not a calorie and that the macronutrient ratio of the food you eat is extremely important for weight loss.  Some of the studies he's been involved with, which I will discuss in future posts, are listed below:

"A calorie is a calorie violates the second law of thermodynamics" in the Nutrition Journal (http://www.nutritionj.com/content/3/1/9)

"Thermodynamics of weight loss diets" in Nurition & Metabolism

(http://www.nutritionandmetabolism.com/content/1/1/15)

This is just basic thermodynamics again!  As a biochemist I tend to side with Richard Feinman.  Biochemical pathways are complex and, depending on the macronutrient ratio of the food you stuff in your mouth, the fluxes through these biochemical pathways will cause the energy to be extracted from your food in a slightly different way (I even think John Hussman will agree as he isn't saying that you should stuff yourself with whatever you like, but just make sure you limit yourself to a specific amount of calories).

The study of human nutrition and weight loss are slowly moving into the quantitative realm where, at long last, computational models exist that can even predict the ratio of fat loss and muscle loss of an individual on a specific diet.  New studies even show that the levels of two peptide hormones at the beginning of one's diet, ghrelin and leptin, can be used to predict whether someone will keep the pounds off (yes, I know this is discouraging)!  I will also make an attemp to discuss all these studies in future posts.

However, even though I am a quantitative scientist and everything that Richard Feinman et al. says makes sense to me, I cannot help but remember the picture that John posted on his website many many years ago where he illustrates how fat loss follows cumulative caloric deficit.  Each time I have overly complex ideas about weight loss and nutrition I tend to revert back to that picture.  It makes me feel better as it says the solution might be simple and elegant.

And it does work for me!  But here I am, fat yet again.  Is it inevitable that I will always put the weight back on? I mean, in a sense we are just machines governed by our bodily chemistry.  And don't go tell me that, because you could do it, I can too.  People are different.