Why is Losing Weight so Hard?: Research Review

Why is it hard and difficult to lose weight
Why does it seem that losing weight is one of the hardest things to do?

If you've ever been or currently are overweight, you know that losing weight can be one of the hardest things you've ever had to do. No matter what you do, you may have some initial success but it rarely lasts. You start to gain back all the weight you lost and sometimes you even gain more. It's almost like your body wants to stay fat.... but why?


OVERVIEW: In this article we’ll look at one of the changes that storing a lot of fat can have on your body and how it can actually make losing weight even more difficult

The paragraphs written in red are a little “sciencey” but I’ve tried to make them a little easier to read. Feel free to skip over them if you’re in a rush. If not, read them all to get a better understanding of what we're talking about.


The research paper I’m going to review in this article is all about a chemical called “oncostatin m”, produced in the fat of people when they become obese. Why this paper? Well, my own master’s degree focused a lot on the underlying causes of obesity and why so many people find it so hard to lose weight, and this paper deals with one of those causes. I also think the difference between brown and white fat (which we’ll talk about here) is pretty damn cool.


In all fairness, I could probably have picked a more widely known topic or paper but this is my blog and I’m going to talk about what tickles my research fancy. But trust me, I think it’ll tickle yours too. Let’s get into it.

What the heck is Oncostatin M?

Oncostatin m (OSM) is a cytokine; a small protein that cells produce, which acts as signalling chemical between cells. It’s made by White Adipose Tissue (WAT) otherwise known as white fat, but only in obese people and has an inflammatory effect on fat cells. The WAT of lean people doesn’t make OSM.



Brown and White Fat?


To understand this paper better we should talk a little bit about the types of fat in the body. When we think about body fat, we’re mostly talking about white fat (WAT) which mostly just stores fat in the body (aswell as producing certain hormones and signallng chemicals… which often cause inflammation in the body).


However, we also have a small amount of another type of fat called Brown Adipose Tissue (BAT). This “brown fat” is much more metabolically active than white fat which means it’s able to burn large amounts of carbohydrate and fat producing large amounts of heat. This heat production is called “Thermogenesis” and is one of BAT’s main functions; it actually becomes more active when temperatures drop and we need to produce more heat to stay warm, using a lot of energy to do so. On top of that, BAT produces it’s own, different, cytokines, which studies have shown to have beneficial effects on our metabolism.


Babies have a lot of brown fat in their bodies which is understandable because it helps to keep them warm, something essential for their survival. Our levels of brown fat drop as we get older but adults still have some and what’s interesting is that our bodies can actually turn white fat into brown fat if we need to. This process is called “browning” and can be caused by drops in temperature or even by exercise.


So to summarize:

  • White Fat: Stores fat and produces inflammation
  • Brown Fat: Burns fat and carbohydrates and produces beneficial chemicals


Let's take a closer look at the study.

The Experiment

This study was made up of the following experiments:

  • Mice fed a high fat diet to make them obese and lean mice to act as “controls”
  • Lean mice fitted with micro-pumps that released OSM into their brown fat
  • Lean mice fitted with micro-pumps that released OSM into their white fat that were exposed to cold temperatures (which causes “browning” of white fat)
  • Isolated, mouse brown fat cells, grown in petri dishes


In all the groups, the researchers measured levels of RNA (the first step in producing proteins like cytokines and enzymes) and proteins themselves, that are related to brown fat activity.


What they found

  1. Firstly, they found that feeding mice a high fat diet and making them obese caused them to produce more OSM in their brown fat. They also produced less Ucp1, an enzyme that cells use to burn energy for thermogenesis. On top of that, they saw more markers of inflammation (specifically Tnf and Ccl2).

  2. Secondly, in the brown fat of mice exposed to OSM (through a micro-pump) they saw more mRNA (the stage that comes before full production of a protein) for the proteins that cause inflammation that we mentioned before (Tnf and Ccl2). There were lower levels of mRNA of proteins essential for glucose metabolism and browning.  On top of that they noticed that the mice were storing more fat as white fat than as brown fat. They also saw lower levels of leptin, a hormone which is important in controlling hunger.

  3. Thirdly, they found that there was less “browning” of white fat in mice treated with OSM, when exposed to cold temperatures. The white fat cells in this group actually increased in size compared to the untreated group. In fact, mice that were not treated with OSM produced 3 times the area of brown-type fat cells when exposed to the cold than the group treated with OSM.

  4.  Finally, in cell culture (in petri dishes), OSM actually reduced the amount of pre-adipocytes (fat cells that haven’t matured into their final form) that matured into fully developed brown fat cells. On top of that, OSM caused brown fat cells to produce less UCP1 mRNA, just as we saw in point 1, above.

In a nutshell

  1. Fat tissue in mice made obese by a high-fat diet, produces OSM
  2. OSM causes an increase in inflammation in fat tissue
  3. The combination of OSM and inflammation:
  • causes brown fat to be less active (less thermogenic)
  • results in lower levels of the hormone, leptin
  • prevents white fat from browning when the body needs it (when it’s cold)
  • makes white fat cells grow larger instead of brown fat


Problems with this study

No study is perfect! There will always be things that can be improved or things that you simply can’t study well in a lab… but that’s science, so we do the best that we can with the studies that we have. You always need to consider the results of an experiment within their context.


My “issues” with this study?

  • These experiments were done with mice or mice cells and while mice have served us very well up until now in studying human biology… they’re just not human and you can’t guarantee that what happens in one animal will happen in another
  • Similarly, what happens in cell culture (in vitro) does not necessarily happen in the living animal (in vivo)
  • Many of the measurements in this study were of mRNA (the stage before a final protein/enzyme is made) so we can’t be certain of the final amount of protein produced (in some cases) under the test conditions 


Why is this Important?

Brown fat carries out some pretty important roles in our body. Because it’s so active, it’s able to burn a lot of calories when we need to to, for example, when we’re cold and need to produce body heat and when we eat too much food and need to burn the excess calories (ever feel your body temperature rise after a large meal?... part of that is caused by brown fat burning some of the excess calories). This is your bodies way of trying to maintain its energy balance (it’s trying to stop you from getting too fat).


Along with that, brown fat also produces some chemical signals that help to control the way we store or burn fat and carbohydrates, something that’s important for how your body deals with excess energy.


If the results of this study apply to humans, it shows that being obese not only makes brown fat less active but also stops your body from producing more brown fat when needed. Less brown fat and/or less active brown fat means your body isn’t as good at burning some of the excess calories that you eat during the day. Long story short, being fat makes it harder to burn excess fat. On top of that, the decrease in leptin might lead to people feeling hungry and eating more which would make the problem worse.


Interestingly, the fact that lean people don’t produce OSM might mean that they can handle eating too much food (on occasion) better than someone who is obese...


A lean person would probably burn off more of their excess calories as heat whereas an obese person would store more as fat.


Life is truly unfair.


So if you're fat, you're basically screwed?

Not quite. Obesity is a pretty complex condition, as the simple state of being fat makes losing weight even harder on many different fronts. What that means is that losing a lot of weight is initially going to be a big challenge (and that’s why so many overweight people have trouble losing weight; their bodies are actually “fighting” to maintain the weight they’re at).


However, there’s no reason to believe that the same changes that make it difficult for obese people to lose weight, won’t start to disappear once they start getting closer to their ideal weight. In my opinion, while losing weight may seem like an insurmountable challenge at the beginning, once you get it down and keep it down, your body will start to “behave” normally again.


In a nutshell, keeping excess weight off will get easier with time (but you need to invest plenty of time and dedication into maintaining good habits to get you slim in the first place). Realistically, that’s what sustainable weight-loss is all about; finding a diet and exercise program that you can comfortably maintain while losing weight. Once you’ve lost it, you’ll have established all the good habits that you need to keep it off.


Eat well, folks.


  1. Sánchez-Infantes D, Cereijo R, Peyrou M, Piquer-Garcia I, Stephens JM, Villarroya F. Oncostatin m impairs brown adipose tissue thermogenic function and the browning of subcutaneous white adipose tissue. Obesity (Silver Spring) 2016 Oct 5 [cited 2016 Nov 10]

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