Posts Tagged ‘diet’

Is weight homeostasis possible?

February 28, 2018

I am slightly obsessed with my weight. Forgive me: I am 58 and have spent many decades repeatedly putting on weight slowly, and then losing it rapidly.

For many years I have wondered why can’t I just eat modestly and trust my body to “sort itself out!”

My recent discovery of the Mifflin St Joer equations (link) has allowed me to  simulate my weight over time, and my calculations are allowing me to understanding my own experience.

But my calculations have also raised a profound question:

  • Is homeostasis of weight even possible?


Homeostasis (or Homoeostasis) is the term given to physiological systems which conspire to keep something constant.

For example, we have systems that maintain our body temperature without any conscious effort. I don’t have to berate myself for being too hot and promise myself that in the future I will try to be cooler.

No. Our bodies sort out their internal temperature. I understand the system consists of temperature sensitive cells and nervous system reflexes that control blood flow, sweat glands, shiver reflexes, and our desire to undertake activity.


And I have generally imagined that in a more perfect world, a similar kind of system would underpin my desire to eat.

In this ideal world, I would naturally maintain my weight without any obvious effort on my part – stopping eating when I had eaten ‘enough’.

I had thought such a system actually existed. One part of the system is supposed to arise from the competing actions of hormones such as ghrelin – which makes us experience hunger – and leptin – which makes us feel satiated.

Together, ghrelin and leptin are supposed to act as part of a system of energy homeostasis.

However, having run many simulations of my own weight versus time (see below) and reflected on this, I am sceptical.

“But I know a bloke who…”

We all know people who seem to be able to eat at their ease and not put on weight.

I have no explanation for that, but then I have never experienced that myself.

My experience is that my weight either increases or decreases over time. What I have never observed it to do in all my 58 years on Earth is to stay the same! (I have written about this before: story 1 or story 2.)

What’s the problem?

I programmed the Mifflin St Joer equations into a spreadsheet to see the predicted effect on my weight of various dietary and exercise choices.

You can download the spreadsheet here and perform calculations about yourself in the privacy of your own computer. 

I entered my current age (58.2 years) and weight (74 kg), and I used the MSJ equations to predict what would happen to my weight if I ate 1800 kiloCalories (kCal) a day.

The results are shown below together with the effect of eating 50 kCal/day more or less

Weight versus Age Projection

  • The red line suggests that if I eat 1800 kCal/day then my weight will gradually decline over the next couple of years stabilising at about 71 kg. That would be dandy.
  • However, the dotted green lines show what would happen if I got my calorific intake wrong by ± 50 kCal per day. This is plus or minus half of a small glass of wine, or a half a biscuit either eaten, or not eaten.

These ‘alternate realities’ predict that my weight in three years time might be anywhere between 64 kg and 77 kg – a range of 13 kg!

To be within a kilogram of the predicted weight, my average energy intake would need to match 1800 kCal/day within 10 kCal a day. That is less than a single mouthful of food!

I don’t believe that any autonomic system can achieve that level of control. 

Weight versus Age Projection 2

So what?

Reflecting on these simulations, I don’t believe that the systems within our bodies that mediate ‘energy homoeostasis’ operate well over many years.

At least they don’t operate well in an environment where calories are so easy to obtain.

So I think my experience of slow weight gain over time is not a fault with my autonomic nervous system, or a moral failing on my part. It is just the way things are.

Asking the thinerati

Asking several slim individuals around the coffee machine this morning confirmed my view. They all were either (a) young (b) self-conscious about fitting into clothes or (c) weighed themselves regularly.

Personally I have resolved to keep weighing myself and using this to provide manual feedback.

How is my weight doing? Thank you for asking. It’s been just about stable since Christmas and I intend to keep it that way!

The mystery of sleep

November 7, 2011

The talk above is by Giulio Tononi, of the University of Wisconsin on “Sleep function and synaptic homeostasis” – stop yawning at the back! Its about 20 minutes long and is comprehensible for around the first 5 minutes.

I have been dieting lately, restricting my calorie intake to somewhere around 1500 calories* per day. I am using the H-plan® diet – where the H stands for hunger: basically the idea is to avoid panic when I feel hungry and just get used to the feeling. Well I am losing weight (of which more later), but the diet has had a side-effect: I don’t need as much sleep. I know that after eating a big meal I would feel especially sleepy, and I wonder if this is just a re-bound from having previously eaten too many large meals?

Normally I sleep for just under 8 hours but crave for more. Currently I am sleeping for 7 and waking refreshed.  I have looked on-line for explanations, or corroboration that this is a genuine effect and found nothing. Why I should feel the need for corroboration of something I am experiencing is something else I don’t understand! But even though it appears to be just me, it certainly lifts my mood.

With my current surfeit of wakefulness, I came across a discussion on Quora about sleep, linked to a talk on YouTube (see top of the page) addressing the fundamental question: What is sleep for? Hearing the basic facts of sleep read out (about 1 minute into the talk) it seemed amazing that we don’t have an answer to the question. Sleep is central to our lives – both personally and as part of of our symbiotic relationship with our spinning planet – and essential to our health. And yet we not know the answer to something so basic as ‘What is it for?’. Wow.

I was reminded of the role of the Sun in our lives. Our lives and cultures are based around the action of sunlight on the Earth, and yet we never look at the Sun directly – it would damage us if we did so. Similarly with sleep, because we lose consciousness during sleep – it evades our gaze.

*1 calorie is a dietary unit of energy approximately equal to 4200 joules.

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