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Probably you know this. You stand on scale and... oh sh*t. What is your first thought? I start excercise! Okay. I start eat less. Cool. But brave promises are easy with full stomach. Self-discipline is tried, when hunger comes. And then we start eat. And that´s good, because we have to. Any diet based on extreme food deprivation is WRONG, because we need adequate amount of food – but nowadays in the era of full fridges and shelves we just forgot how much we need food. So before we start eating we have to consider and control two things. WHAT we eat and HOW MUCH is enough. But HOW do we know HOW MUCH is enough... when we are still hungry, but we have still too much fat storages?! What hunger is and how is it created in our brain?

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What holds us back

I tell you a story about what is happening when we are hungry. Our stomach is empty and it shrinks. Subesquently ghrelin, called also „hunger hormone“, is secreted. Ghrelin starts to bind to receptors in our brain and brain starts yelling stupid ideas: „I´m hungry! Eat that cake! It´s fast source of energy!“ And of course we eat it and we are grumbling with full mouth about how we can start tommorow. But story continues...

Our digestive enzymes dissolve macronutrients in cake mostly on glucosis and through intestine wall is glucosis absobed to blood. But glucosis can´t stay in blood forever – if it happens, for example during diabetes, it causes a lot of health problems. But in healthy body we have some receptors or sensors of glucosis level in the blood – beta cells in pancreas. They reacts on high glucosis level in blood by excretion of insulin. And what is function of insulin? The thing is, glucosis on it´s own can´t be absorbed by cells – so insulin helps to enter glucosis into the cells. If we go running after sweet pleasure, insulin with hands full of glucosis is knocking on muscle cell´s doors and we are burning recieved energy. If we are sitting and resting, it´s quite more difficult situation. Our basal metabolism (mostly brain, but also muscles, organs etc.) consume some portion of this energy, but when it´s too much, insulin starts to knock on to liver, where excesive energy is stored (as glycogen) for bad times. But liver is not bottomless well of course. When it´s full, insulin starts with storing energy for very bad times. To fat. If the cakes (or any other kind food which amount exceed caloric intake/expenditure) were already some, and this is your routine for a few days/weeks/months (based on your metabolism) and you are not a bear preparing on a winter (based on actual season), you have a problem.

Okay we got fat - what next?

During some time of hedonistic eating or few dozens small sins our fat storages are slowly expanded, but nothing is lost yet. It´s time for leptin, produced by fat tissue. Basically, more fat we gain, more leptin is generated. It has also receptors in brain and when fat tissue is gaining weight under our skin, our brain starts to give us a good advice – „Okay, this was last bite, we have enough!“ And our appetite is decreased.

When things go wrong...

We eat, but ghrelin is still high and we are still hungry. Levels of insulin and glucosis are beyond the normal values, but cells are without energy and we are tired (maybe winter´s comming). Fat is too much, leptin is pouring from our ears, but our brain is telling us to eat even a plate.

Imagine that your phone is ringing. You answer, don´t you? Exspecially, when you see the name of person you know. What happens if he/she starts to call more often? Few times you pick up the phone because you were well-behaved, but if this person is still calling, it starts to bother you. Phone is ringing every moment and you´re loosing your mind. After few calls you stop answer, start ignore it and probably even turn down volume of your phone.

And this example ilustrates the problem of resistance. If the cells are constantly shooted by „ringing“ of this hormones, they adapt and start ignore these signals. And we´re gaining fat. It´s important to note, if we start solve these problems with maintaining of our diet plan and excercising they´re reversible in the begining (more info in the resources).

Mice with backpacks, without bones... enough internet for today.

In the beginning of this year a new mechanism of maintaining weight was discovered. First was the question – why people with sedentary lifestyle are prone to gaining weight, even when all hormonal mechanisms mentioned above are working properly? It was hypothesised, there is other mechanism connected with standing. What (or where) is difference between standing and sitting?

For revealing the truth, mice was used once again. Scientists implanted them weights with different weight under their skin in abdomen or back and give them free amount of food. Surprisingly, mice with weights started to eat less in compare with mice without weights, and subsequently they lost fat. But this wasn´t end. Scientists are scientist because they often ask „why?“. Based on the assumption that osteocytes (type of bone cells) can detect changes of body weight, they started to suspect bones as participants in this mechanism. They depleted osteocytes in mice and effect of loosing weight by carrying weights disappeared. This newly revealed mechanism was called „gravitostat“. As every homeostatic mechanism, it has to have some sensor, and based on this findings, this sensor is located in bones of lower extremities bearing whole body weight. If this mechanism is presented in humans, strained osteocytes in leg bones inform brain about changes of weight and it regulates this changes by negative feedback through maintaining of food intake. So it seems, gravitostat is cooperating with leptin on fat reduction.

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So if you have problems with loosing weight, but you eat well and excercise regularly, probably you should think about that what are you doing during the rest of the day. Of course we all have a lot of responsibilities at work or at school, where we have to sit. But maybe isn´t bad idea to use stairs even we have elevator in the building, or make a few steps after lunch. So if you are finished with this article, take a small walk and stimulate your gravitostat.

References:

https://en.wikipedia.org/wiki/Ghrelin

https://en.wikipedia.org/wiki/Insulin

https://en.wikipedia.org/wiki/Leptin

http://www.pnas.org/content/115/2/427.full

Something more about reversion of hormone resistance:

https://www.ncbi.nlm.nih.gov/pubmed/17339026

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3767170/