Weight loss is something I talk a lot about. Not because I actively bring up the topic- to be honest its something I'd like to have to hear less about. But really, there are so many theories on the topic and just like the X-files- the truth is out there, somewhere ( just don't ask Kim Kardashian for directions because all you will get is weird tea and a waist corset....) I digress. Given that food plays such a big role in the Weight Debate, I thought I would take a bit of time to look deeper into what it going on when you try to lose weight.
There are many jiggly bits to talk about when covering this topic, however I am just going to cover the changes which occur hormonally when we lose weight, to set the scene for other vectors at a later date. Namely we're going to look at the role that a hormone called leptin plays in weigh regulation.
I going to use my mate Kim K as the example throughout as the poster girl for weight loss attempts.
So Kimmy wants to lose weight. She sees the latest diet guru who puts her on a low calorie diet and gets her training like she's getting ready to be in the next Gladiator movie. After an arbitrary 12 weeks, Kim looks fab! She has lost inches, is pumping more iron than Arnie and is running loops around Kanye. In short she is harder, better, faster, stronger.
Yes- big calorie deficit will get big results, but why don't these big results hang around? Let's have a look at what was is probably happening while Kim's amaze-balls transformation was happening!
There are a handful of hormones which we currently know are associated with weight maintenance, which I will outline in a mo. But first I want to introduce the concept of 'homestatsis', as it is a concept which is crucial to understanding why approximately 80% (depending on where you read it) of weight loss attempts not only end in weight re-gain, but often over shooting the starting weight.
To put it bluntly, our main aim in life is not to die, well from a biological/survival of the fittest point of view anyway. Homestatsis is the concept by which our body attempts to control this. In a nutshell, our body is in a constant state of assessment and adjustment to make sure we stay in equilibrium (balance) and alive. If we get too hot, we slow heat production and go into cooling mode- think sweat and warm skin . If we get too cool, we shiver to produce heat and get goosebumps to try and reduce heat loss. There are lots of different ways our body works to keep us alive and we don't even have to ask. Cheers body, nice work on the homestasis.
Our weight is also under homeostatic control to a point, because if we lose too much weight, we can die- so we need things in place to avoid the whole death situation. If we gain too much weight, well, we don't seem to care as much about this, but there is some attempt at controlling this part too. This is likely because during our evolution to date, over eating hasn't really been a threat to life, where starvation has been, and therefore we are better geared to protect against weight loss than we are weight gain. And here starts the problem.
As I said earlier, there are a set of hormones we know are associated with weight maintenance. There are probably more we don't know about yet, and there is also other genetic and environmental factors involved too, but for now let's keep to the hormonal component.
Leptin, Ghrelin, T3 Thyroid hormone, insulin, POMC, peptide YY, cortisol and perhaps a touch of testosterone as key players in the complex hormonal regulation of weight . A hormone is a signalling molecule released by a specific gland, which is used to help regulate us- keep us in homeostasis- by triggering a reaction somewhere else in the body. Think of a king (the gland) sending out a messenger pidgeon (the hormone) to send the message to the village (the target tissue) to start building the city wall (the change needed to protect the body). For more reading on glands and hormones check out this site. I could write an essay on each- perhaps another day.
The 'set-point' theory is probably the best explanation we have at the moment to help us understand weight gain after weight loss. When we lose weight we lose both body fat (BF) and lean muscle mass (LMM). Our bodies detect a shift in body composition and past a point, our 'set popint', starts to sense danger. Starvation means death is a possibility, so measures are put in place to slow, or stop this progression into perceived starvation. The technical term for this is adaptive thermogenesis, where we become more efficient in using what little energy we are given. Leptin is in the centre of this shift into fat preservation.
Leptin is the 'satiety' hormone, or the 'no thanks I'm full' signal, which is secreted by fat cells to tell the part of the brain (hypothalamus) that we have enough energy stored as fat to keep us out of any danger of starvation. Grehlin is the opposing hormone which is triggered to counteract weight loss and drive hunger signals so we eat more and move away from starvation. In a normal healthy humans these hormones play nicely so that we are weight stable, adjusting for any major changes. However when we create large energy deficits when dieting, we are triggering a response which sets into drive the need to seek out food for survival. We become more motivated to find food, we are less satisfied by what we do eat and tend to serve up bigger portion sizes.
To add to this, when we diet our metabolic rate goes into a lower gear, so it can retain as much fuel as possible, not knowing how long this restriction will last. We lose fat cells, which secrete leptin, and therefore reduce leptin production capacity, which triggers the brain to go searching for food. Cue ghrelin- the hungry hippo hormone. It is secreted in larger amount to drive all this diet breaking destruction.
So to continue the Kardashian theme, Kim has done really well for herself to lose that weight, but at the end of filming Handbag Gladiators, she is no longer compelled to keep up what she has been doing and slides back into her old eating habits. Nek minute, Kim has put back on the weight she lost, plus a few kg's more. Disaster!
The unfortunate thing is, that it appears that if or when we regain the weight we have lost, we can remain in metabolic slow-mo, while eating the old amount of calories, meaning we are less efficient than we used to be, and run the risk of overcompensating and being heavier than when the we started. This appears to happen, in part, because our bodies want to get fat AND muscle protein stores back to where they were in the 'safe' zone. In getting there, we are much faster at putting on fat than muscle, so our hormonal drive to refeed is active until both levels are back to the start. So when we meet out previous body fat levels, there may be a lag period before muscle protein homeostasis is reinstated. DOH! To make matters worse, while it is hard to assess, it appears that the slowing of metabolism is not just while we regain weight, with one study reporting similar metabolic efficiency one year after weight loss. Meaning adaptation is slow and not really in our favour.
Does this mean we should all throw in the towel and give up? Not necessarily. The key appears to be making changes which are sustainable. In essence, we need to be looking towards a LIFESTYLE change which supports maintenance of any weight loss, and avoiding drastic, short term measures. If the changes that were made to elicit the weight loss can be carried on, through changes in attitudes towards food, support of family/friends/workplace and maintainable levels of physical activity, then, although we might be running a bit slower, we stand a much better chance of keeping it off permanently! Hoorah!
So this is just a small snap shot into how and why weight loss attempts may not work. It is a fairly complex and multi-faceted situation, so it would be naieve to think this was the one and only answer. However knowing this can help to inform the directions we take when trying to lose weight successfully- i.e. losing it and keeping off.