T Nation

Calories (In vs Out) - Thermodynamics

I work at this gym now as a PT and one of the head honchos who comes in to all the difference clubs to teach the trainers was explaining the Law of Thermodyamics. Here’s what it kind of went like:

Him: “If your BMR or maintenance level is say 2000 calories and you accidentally screw up a day and binge late at night and eat a piece of chocolate cake 1 minute before you go to sleep for 8 hrs. Will you lose fat assuming you only ate 1900 calories that day?”

Me: “No, because you’ll probably screw up your blood-sugar levels, which were already low, and have a spike in insulin followed by a drop. The carbs and fat won’t be used as energy but will be stored as fat, right?”

Him: “Well, actually since you eat less calories than you burned, you will lose fat. It’s the law of thermodynamics.”

Me: “Ok, so you might lose weight, but wouldn’t it be muscle instead of fat since you’re eating below your BMR?”

Him: "Not necessarily. Although, protein, carbs, and fat %'s are important, it basically comes down to CALORIES IN VS CALORIES OUT.

Okay, it didn't go exactly like that, in that order, but you get the idea of his thinking and mine. Who is right here? Are we both right to a certain extent? These people I work with think they're way is the only way and are all high-carb people with an intense hatred for low-carb people. They're also putting 180 lb. women with 30% bodyfat on a 1500 calorie diet of 65% carbs. They can eat whatever they want so long as they're ratios and calories stay constant.

Is this all bogus or what? These people are such good salesman that I’m almost convinced that they’re right and I should go back to training like a sissy and do cardio. What’s up?

I am majoring in Chemical Engineering, so I know thermodynamics. It’s pretty much rehashed in every course I take. The first law of thermodynamics states that energy is conserved, that it can neither be created or destroyed, merely converted from form to another. Mass conversion to energy, E=mc^2, is not covered in this but will concel with a mass balance. He is making a comparison of the conservation of energy (potential, kinetic, internal, enthalpy, work, and heat) and losing fat because you consume less energy than you expend. From where does this loss in energy come? Well the body gets energy from a variety of substances. Simplistically, the sources are protein, fat, and carbohydrates. To be used as energy they must be converted into a form the body can use. Each has a different efficiency of conversion to energy because there are a variety of mechanisms. So to say that you WILL NOT get, or stay, fat from consuming less than your calculated BMR is totally false. What is true is that you lose STORED energy such as glycogen, proteins, or triglycerides. The body will mobilize these stores to try and maintain an equillibrium in energy.

You must also consider that mass and energy are moving in and out of the system, the body. You must then choose a period of time in which to evaluate the system. Since the body does not run like a smooth steady-state system, because it is constantly changing, the best way would be to monitor an infinite amount of intervals over the entire day. Let’s say that you are using 100min intervals. Well during that first 100 min you could consume more calories than you expend. The body will store these extra calories as proteins, triglycerides, or glycogen. If the glycogen stores are full then you are out of luck because you’re now getting fatter. During the next 100min you could consume less calories than you expend. Now you’re losing stored energy. If glycogen stores are low then you are losing proteins and in respect getting fatter.

It seems I accidentally posted before I finished.

Over the course of a day these all add up. You could still have a net loss of calories while getting fatter in respect to the beginning, though you will most likely have less mass. Ask this person what would happen if people consumed the 1900 Cal in one meal per day. They are still consuming less than the calculated BMR. Another thing, the BMR is not the same under different conditions. For example, if it is colder outside than the body it will produce heat by expending energy. This because there is energy transfer at the system boundaries, hot goes to cold. This means there is a net loss of energy. The energy loss is also greater than you expect. The body needs to expend more energy because its optimum equilibrium temperature is 98.6 F. In colder situations there is already heat moving to the surroundings so more must be produced to keep the temperature up.

To conclude, here is what you need to know. The body is not a steady-state system, there is heat transfer across the system boundary, and work can be produced and lost (Hint, your body does perform work and the BMR is inherently inaccurate for these reasons stated above). This is still neglecting the potential, kinetic, internal, and enthalpic energies. I assume he won't know what these are anyway so the above should suffice. Remember though, the storage or mobilization of energy is dependant on the current state of the system since it is not steady-state. This is all just oversimplification because the body is much more complicated than this but you can see where I am going. Anyway, if you have problems confronting this individual then just ask about his background. Does he have any knowledge of biochemistry, biology, endocrinology, heat transfer, and/or a variety of other sciences that would explain this phenomenon? Or is he just spouting rhetoric from some personal training manual? Obviously he is not well versed in any of these areas and if you speak to him again you will realize you have much more "expertise" in this area.

He is “more” right. While blood sugar and hormone control are important to losing as much fat as posible and maintaining muscle THERMODYNAMICS are the main factor of weight loss.
If you go on a low carb diet but eat 500 cals a day over your BMR you won’t drop weight.
On the other hand somebody with a normal metabolism will lose a signifigant amount of fat over time if they simply eat less.

Overall a diet that watches carb content and or Insulin will lead to greater fat los FASTER and a higher protein diet will ofcourse lead to preserving more muscle than a high carb diet.

Keep in mind that a way to lose weight is through caloric restriction. If you burn more calories than you consume, you will be in a caloric deficit. While low carb diets allow some individuals to get leaner, they are not necessarily performance enhancing. I have a difficult time putting forth high levels of energy if I restrict my carbs. Look at the other guys point of view. If you have an overweight female who is likely untrained, and place her on a restricted calorie, low carb diet, she is probably going to feel a lack of energy and desire to do the exercise she so desperately needs. If you simply restrict her calories, and let her keep the carbs moderately high, she will have more energy and drive to start and complete a weight loss regimen. You have to consider the training level of your clients. A low carb approach will likely be much more effective to someone who is highly trained and used to the rigors of dieting.

In my experience the most “confident” people in this regard are usually the ones who know the least. When you are so dogmatic you have no time or inclination to evaluate other opinions so therefore they just become “wrong”. The less they know, the prouder they are to convince you that what they do know is correct…


About the calories in vs out, here is my take. Calorie balance is important so if you’re grossly off on a daily basis your physique will of course change. But calorie in vs out is not the only thing. These “health professionals” dont know physiology and biochemistry well enough to understand that there are acute effects related to food intake. Like substrate storage, hormonal response, etc. So by their argument, if your needs are 3000cals per day, then if you just ate a big breakfast of 3500cals to gain mass, you will gain mass. I agree, but the acute effects of that meal dictate that you will lay down a whole lot of fat after that meal. The muscle can only take up so many nutrients per feeding. Why not feed the muscle and then stop rather then feeding the muscle and fat and then hoping that the fat will get mobilized later and you wont get fatter. Also youve gotta realize that metabolic rate shifts with fasting or feeding. So if I go 3500cal per day in the breakfast meal then fast till the next breakfast, my metabolism will be slower for the next breakfast and I will be more likely to store more fat!

Hi Scott. Well, first off, the example you talked about with the PT is too simplistic to offer any help to anyone on an individual basis. Neither one of you is right, but I agree more with your perspective than the other. Newton’s laws of thermodynamics don’t accurately describe the interaction because it’s too complex to just say calories in vs. calories out (You’re right about the brilliant salesmanship, even if the guy’s a dunderhead when it comes to biophysics). Some people can actually eat like that and not gain a pound. I used to, and I couldn’t gain a pound even by forcefeeding with this kind of diet until I hit 40, my metabolism was so fast. My thought is that if you give ten people a hi-carb diet with these nutrient ratios, you’ll get ten different results. Then factor in circadian hormonal changes affecting metabolism, per your example, and you really won’t be able to tell anything about the diet at all.

Except… I wouldn’t want to be those fat women on a high carb diet, per se, even if it is only 1500 Kcals. 1 in 10 will benefit from it, all the rest will stay fat, athersclerotic and pre-diabetic. Americans have been on a high carb, low fat diet for the last 20 years, and all it has done is increase rates of obesity, heart disease and adult-onset diabetes nationally.

Oh I forgot to add ('cuz I didn’t really answer all of your questions)…

I read some research done in the last century about calorie intake, weight gain and consumption at different hours of the day. The study came down to some very simple conclusions. If you lead a sedentary life, if you are desk bound and exercise very little, the later you eat the fatter you’ll get. The worst case example was the typical businessman who eats black coffee, OJ and a roll for breakfast (hi-carb diet, right?), a sandwich for lunch and an enormous 3 or 4 course dinner most nights. This guy will invariably get fat, even though he probably isn’t eating more than 2000 cals/day. Blood sugar spiked up and down throughout the day, and the test subjects felt terrible.

At the other extreme were similar types who ate an omellete, sausage, toast and milk for bkfst, big roast beef sandwich and milk for lunch, and a salad w/tuna for dinner, say. These people don’t get fat even though their cal intake is higher, and their blood sugar stayed almost constant throughout the day. They felt fine. Another thing this study found was that if you eat protein with some fat for your first meal of the day, no matter what time you eat and it really is your first, then blood sugar rises slowy and stays pretty much constant all day long. If you have carbs and no protein, your blood sugar will spike up and down throughout the day no matter what you eat at subsequent meals. I’ll stick to a hi-pro diet myself…so where’s my steak?

question for John M Berardi.

John you wrote 'why not feed the muscle and stop rather than feeding muscle and fat' is there a guide to how many calories you should consume in a given meal to feed just the muscle and not fat?

Lew, that’s a good question and the answer is no. I guess the point of the comment was that if you overconsume calories you will be “feeding the fat”. I like to think that you’re safe if you split up your daily requirements into 5 or 6 meals, you will be safe.

Thanks for your replys fellows. I understand that everyone is different and burns different amounts of calories. Quick question though. For an obese female, 30% bodyfat, who weighs 212 lbs. would a diet of only 1,500 calories be bad. I mean isn’t that like underconsuming too much. A trainer at my club just put a client is similar to the stats above on a 1300 calorie diet with every 5th day being 1800 calories. Carbs 60%, Protein, 20%, Fat 20%. From my understanding, BMR can be simply calculated (although it will not be correct) by multiplying bodyweight by 16, 17, or 18. So for example, say we multiply 16 x 212, we get about 3400 calories. However, this person is obese, moves less in the day so probably burns fewer calories. Maybe her BMR is 2500 at the least. Wouldn’t a 1500 diet be too extreme and the woman would end up losing some fat but more muscle?? And worst of all, her metabolism will slow down and she’ll gain it all back and more, right? Please offer more help if you can.

At 212# and 30% bf, that’s about 140# LBM (quite a bit for a woman, but maybe she’s tall and/or muscular and/or carrying lots of water… or maybe the body comp wasn’t terribly accurate as they tend to lose accuracy at above 30% bf). According to John Berardi’s RMR calculation provided by Nate Dogg in the “Massive Eating by John Berardi” post, this woman should need almost 3000 calories per day to maintain. If you buy the never-go-1000cals-under theory, she shouldn’t be taking in too much less than 1800 calories per day.

Because of Mr. Berardi I now realize that in the past I’ve been too restrictive with calories while dieting. Using his RMR formula and hacking off between 500-1000 calories per day seems like a great idea. I’ve only been doing it for a couple of days, but it feels good and I’m strong in the gym (I usually experience an immediate drop in energy when I begin dieting).

Scott-
The ‘head honcho’ is not correct in this case. In fact, my opinion would be that your arguement shows more education. It all DOESNT come down to net accumulation or expenditure of calories, at least as far as the type of change this will bring about in your body. Each meal you consume has a certain amount of calories associated with it (in fact, these are really kilocalories, if you want to get technical). This number relates the amount of energy which will be released from very specific bonds when the food you eat is broken down. You should also consider, that all the calories in a large meal may not be digested, and may to some degree ‘pass through.’ Now, if the total energy extracted from the food you eat in a certain period of time outweighs the energy expended by your person in this same period, then there will be a net increase in energy in your body – still in the form of these bonds, basic molecules will form as biopolymers and be stored as fat or sugar-based polymers. However, just because you may use more energy in a day than you consume does not necessarily mean that fat stores are being accessed for this energy. In fact, if you follow a 60-90 minute workout with an 60-90 minutes of cardio, blood sugar levels will be depleted, (perhaps even blood fats will be depleted), and muscle will be used for energy. Now, you have created a catabolic environment within your body. This state will fuel weight loss, but not the kind of weight loss that you will see as a desired change in your physique. Also, since your body is not a relativistic system, you do not convert between mass and energy. When energy is needed, for example in this case sugars, alpha 1-4 linkages between sugar monomers and others are broken (like links on a metal chain), the energy released is used by the body (ever felt how warm a material can be after causing it to deform ?–chain anology), and the basic building blocks from this biopolymer (individual links) pass through your system, weighing no less than when they were first ingested. you see, you can combat any falacious arguement when you look at your body as an interplay between a thermodynamic system AND a chemical system. Obviously your boss doesn’t see this coupling.
Tell your boss to contact myself or John U next time he’s in Atlanta – I know a few professors i had as an undergrad who would be very quick to teach your ‘head hancho’ a thing or two.

Scott, I just wanted to sum up a little. It certainly appears to me that the issue is way too complex to distill into a single “formula” for everyone. While blanket statements and formulas are certainly comforting and offer some intellectual stability, it’s really just pablum to sell something to the masses, which is why BFL went #1 on the bestseller lists for so long. If I can see any common thread in this discussion so far, it’s that JB’s formula is an excellent place to start, but you’ll need to help this women tailor her diet for her needs and issues as she progresses in her weight loss program. Good luck with that, and just hit your boss over the head with a book (if he owns any) or something.

TO EVERYONE ELSE: Excellent and impressive discussion! Let’s keep it going like this.

What everyone seems to forget is that the vast majority of the regular public (not the gym rats) are overeating. The average person under reports by 10%, and the obese by 40%. They eat a half a box of pasta and count it at 1 serving. There are 8 servings in a box (so they say)…For the average over weight individual, a caloric defecit will get them to drop a few lbs. I’ve done it with a bunch of clients. Let them eat the foods they like, so they don’t dive off the deep end, just control intake, vs, output…You can’t explain insulin spikes to them, they don’t want to hear it…they want to lose a few lbs with the least amount of discomfort…