Negative feedback loops, Tolerance, Dependence & Withdrawal.

I couldn't find the plot that I was looking for, but this electrical plot is equivalent.

From http://www.tpub.com/neets/book9/37k.htm

e_A represents the amount of a substance that perturbs one of the body's negative feedback loops. The amount oscillates between 0V & 100V.

e_R represents the effect of the substance on the body. 100V represents maximum effect and -100V represents maximum anti-effect.

The very first time that the substance is taken, there is 100V of effect, initially. As the time-constant of the negative feedback loop "kicks-in", the effect decays exponentially. Just before the substance is discontinued, the effect is down to 36.8V. Just after the substance is discontinued, the anti-effect is -63.2V. If the input continues to oscillate between 0V & 100V, the effect & anti-effect eventually become equal in magnitude. This is known as "cycling".

If the substance is applied continuously, the effect decays exponentially to 0V. When the substance is discontinued, the anti-effect is -100V initially, but decays exponentially to 0V.

This is analogous to drug tolerance, dependence & withdrawal, where eventually, the user has to take the drug just to feel normal, and discontinuing the drug gives the worst withdrawal symptoms ever, initially. After the drug has been discontinued for a while, the withdrawal symptoms decay exponentially to zero.

The above also applies to supplements that perturb one of the body's Hypothalamic Pituitary NFB loops e.g. the HPA (Adrenal), the HPG (Gonadal) or the HPT (Thyroid) Axes, or any other system (as everything in the body is regulated by a negative feedback loop).

This explains why a supplement can work really well at first, then its effect decays exponentially, until there is zero effect. The loop has compensated for it.

EDIT: If a loop is broken, due to zero secretion of one of the hormones controlling it, then a prescription drug/hormone restores the loop's output level to normal. E.g.

1) Prednisone for a broken HPAA (primary, secondary or tertiary hypoadrenalism) e.g. Addison's Disease.
2) Testosterone (men) or progesterone (women) for a broken HPGA (primary, secondary or tertiary hypogonadism).
3) Levothyroxine for a broken HPTA (primary, secondary or tertiary hypothyroidism) e.g. Hashimoto's thyroiditis.

I'm on 2) & 3), due to a broken pituitary gland. Luckily, it's not completely broken, so I don't need 1).

Nonequilibrium thermodynamics and energy efficiency in weight loss diets, by Richard D Feinman and Eugene J Fine.

From http://www.caloriegate.com/the-black-box/9-pictures-that-prove-beyond-a-reasonable-doubt-that-calories-dont-count

From Nonequilibrium thermodynamics and energy efficiency in weight loss diets:-

"Conclusion
Emphasis on kinetics and nonequilibrium thermodynamics provides a conceptual framework for understanding the effect of macronutrient composition on maintenance and change of body mass and possibly for analysis of adipocyte metabolism in general. The simple model presented is intended to be consistent with a general shift away from equilibrium thermodynamics and towards a more dynamic analysis of cellular processes."

Sounds plausible. There's only one thing wrong with Feinman et al's article - it's completely wrong!

Consider two rooms:-

Room "A" has an adjustable heater. The heater is adjusted until the room temperature is 20°C.

Room "B" has a radiator, controlled by a wall-stat set to 20°C. The radiator is on, and the room is at 20°C.

We have two rooms of the same size, at the same temperature.

If you plug in & turn on a 2kW fan heater in each room, what happens to the temperature in each room?

Room "A" gets warmer, because there is 2kW more heat power entering it.

Room "B" stays at 20°C, because the wall-stat reduces the heat power from the radiator by 2kW.

The human body stays at 37°C ±~2°C, because there's a Negative Feed-Back loop adjusting the heat power produced, via UCP's, futile cycles, thyroid hormones, shivering and heat conservation/wasting behaviours.

∴ Variable heat power generation due to variable Dietary Efficiency doesn't change E_out.

EDIT: By request, here's Figure 1 from the above study.

This suggests that fat mass & therefore weight can increase indefinitely - at maintenance energy intake, due to the effect of insulin on HSL. This, of course, is quite impossible!

From The Energy Balance Equation:-

Change in Body Stores = E_in (corr for digestion) - E_out (BMR/RMR + TEF + TEA + SPA/NEAT)
__BMR/RMR & TEA ∝ weight
∴ ↑ weight → ↑ E_out
__If E_in = constant, ↑ E_out → ↓ (E_in - E_out) → ↓ weight
∴ ↑ weight → ↓ weight
∴ Figure 1 is wrong.

Why Calories count (where weight change is concerned).

I have to add the words "where weight change is concerned", as calories have little to do with body composition or general health (unless somebody becomes morbidly obese).

From https://docs.google.com/file/d/0Bz4TDaehOqMKSXZHUUVxWnl5VTQ/edit?usp=sharing

Arguments used by Calorie Denialists include:-

1) Calories don't count because the human body isn't a Bomb Calorimeter and treats different macronutrients differently.
 
100g of liquid paraffin burns in a Bomb Calorimeter, yielding 900kcals. In a human, it passes through completely undigested. Ah-ha!, I hear you saying. This proves that the Energy Balance Equation is invalid. Uh, nope!

Calories in = Calories entering mouth - Calories exiting anus

As 100% of liquid paraffin calories entering the mouth exit the anus, Calories in = 0

This is why Sam Feltham's "Smash the Fat" "experiment" is nonsense. A high percentage of the large amount of raw almonds he ate would have exited his anus incompletely chewed, undigested & unabsorbed.

See the picture above? In the late 1800's, W.O. Atwater established Atwater Factors (3.75kcals/g for digestible Carbohydrates, 4kcals/g for Proteins, 5kcals/g for Ketones, 7kcals/g for Alcohols & 9kcals/g for Fats*) using Human Calorimeters, not Bomb Calorimeters. Atwater Factors are pretty accurate.

*Fats containing different fatty acids have slightly different kcals/g. Fats containing long-chain fatty acids are 9kcals/g. Fats containing medium-chain fatty acids e.g. coconut oil are ~8kcals/g.

For more information, see Calories ...


2) Calories don't count because Dietary Efficiency varies for different macronutrients.

Uh, nope! The Heat Power generated by the body is regulated by a NFB loop involving the Hypothalamus, Pituitary, Thyroid Axis, also Uncoupling Proteins (UCP's), also shivering, so as to maintain a body temperature of 37°C ±3°C. If this wasn't the case, different amounts & types of foods (also, changes in ambient temperature & clothing) would cause large variations in body temperature resulting in death, as the enzymes in our bodies function correctly over a limited range of temperatures.

Heat Power generated by the body (W) = Temperature difference between the body & ambient (°C) divided by Thermal resistance between the body & ambient (°C/W)

∴ Dietary Efficiency is irrelevant.

How a B.Sc.(Hons) in Electronic Engineering is relevant to Diet & Nutrition.

The human body regulates various processes using negative feedback loops. Here's blood glucose regulation.

From http://www.studyblue.com/notes/note/n/ch-47-chemical-signals-in-animals/deck/3085387

Here's a generic Hypothalamus-Pituitary-X Axis loop, where X may be thyroid, adrenal, gonadal etc.

From http://www.studyblue.com/notes/note/n/ch-47-chemical-signals-in-animals/deck/3085387

Electronic Engineers understand how negative feedback systems work, such as phase-locked loops & amplifiers.

Negative feedback control systems can overshoot, especially if there's a delay in the feedback path that's longer than the rise time of the input step.

An example of this is the first-phase insulin response. Loss of the first-phase insulin response occurs in over-fat people who are hyperinsulinaemic. Without the first-phase insulin response, there's a delay between an increase in blood glucose and an increase in insulin secretion. A rapid upwards step in blood glucose (say, from eating a high-GL meal) causes a massive overshoot in insulin secretion, resulting in postprandial sleepiness, also down-regulation of insulin receptor activity in the appetite centres of the brain, causing ravenous hunger when the insulin level falls to normal.

See also Blood Glucose, Insulin & Diabetes.

People shouldn't be too quick to write-off the knowledge of an Electronic Engineer who's delving into the mysteries of the human body.