The Hormone That Keeps Us Fat!

Ever wondered why you get to a certain level of body fat and no matter what you do, you just can't lose any more weight? This article explains why!


Set point, quite simply put is the body’s way of physiologically regulating your bodyweight at a certain level. There are various internal processes our body has that make a coordinated effort by your body to adjust the intake and expenditure of energy so that a specific amount of body fat is maintained. Any attempt to deviate from the pre-determined level will be actively resisted. Looking at the set point in more detail tells us that a regulatory system exists in our body that is designed to maintain our bodyweight at a fixed level.

This is similar to other systems that we have in our body that regulates our blood glucose levels, and our body temperature at a certain level. The body will attempt to protect against you being too heavy or your becoming too thin by a mechanism in the hypothalamus in our brain called the Adipostat.

The Adipostat

The Adipostat establishes a set point for a fixed amount of fat in our body. The brain attempts to maintain this set point by regulating our expenditure and storage of energy until our fat stores meet the level determined by the body.

A person who has been dieting for many months will have their efforts undermined by the body working to restore the bodyweight to its set point. The Adipostat does this by activating the sensation of hunger so that we feel the need to increase calories or by slowing the body’s metabolism which will cause a weight gain.

Just because our body will maintain this stable amount of body fat at a certain level doesn’t mean that we can’t change this level. We can change our body fat levels by a combination of the type, and also the amount, of physical activity that we perform, and the level of nutrients that we eat.

The Hormone Leptin

Although a negative energy balance from either fasting or exercise causes a fall in the levels of an important regulatory hormone called leptin, while a positive energy balance with glucose metabolism is important. Leptin is a hormone that is secreted by fat cells that influences energy expenditure and food intake through neuroendocrine pathways. The most important lifestyle factor that can lower this set point more than any other is by performing regular exercise.

The lifestyle changes that should be made should be of long term changes and not just short term such as just trying to lose a few pounds for a holiday or some other event. As already mentioned above, our eating patterns are regulated by feeding and satiety centres located in the hypothalamus and also by the pituitary gland that responds to the bodies signals indicating high fat stores and hunger. Substances that are critical to this process include glucose (sugar), insulin and leptin.

Rising levels of leptin appear to suppress the appetite and falling levels stimulate appetite. Overweight people tend to have higher levels of leptin and these leptin levels fall as bodyweight is lost. This system works as a self balancing biological mechanism, particularly to prevent starvation by stimulating the appetite as bodyweight is lost, and to reduce the appetite as weight is gained.

When leptin levels fall this sends a message to your brain that you are in a starvation mode, which then sets off a reaction which will decrease your metabolism thereby burning less body fat, breaking down your muscle mass and starts storing body fat and increasing your appetite. These normal responses are necessary to keep us alive even with severe calorie restriction, but make it harder to keep losing our body fat.

Leptin levels are affected by several factors. Leptin is secreted by fat cells and the more body fat we have, the higher the leptin levels, but as our body fat stores decrease, leptin levels also fall. Leptin levels also correspond to your calorie intake, when you cut calories the leptin levels also decrease. Leptin levels will fluctuate along with insulin, the hormone that is released by the pancreas that works to keep your blood sugar levels stable. When your insulin levels are low, such as when someone embarks on a low carbohydrate intake, the leptin levels decrease. So you can see that when calories are cut aggressively to lose body fat and/or you reduce carbohydrate intake the harder it becomes to lose the body fat which means that body is working against you.

Lowering and Maintaining Low Body Fat

Method 1: The Cheat Day

Cheat mealThere are ways of lowering and maintaining low levels of body fat. One of these methods requires one day of the week as a cheat day where you can eat virtually anything you want including your favorite foods that you have left out of the diet. Anything within reason can be eaten including sugars and fatty foods. This cheat day serves two purposes. One, is it helps you to stick with a certain eating plan due to the fact that you know on this day you can satisfy any cravings or temptations that you may feel on the calorie restricted days. The second purpose of the cheat day is that it stops the normal dieting plateau which normally occurs with calorie restriction. The dieting plateau is brought about from the set point mechanism that is mentioned earlier in this article that physiologically regulates your bodyweight by adjusting the intake and expenditure of energy so that a specified amount of body fat is maintained.

The main problem with calorie restricted diets is it puts the body into a starvation mode which invokes hormonal processes mentioned above, to slow the metabolism and increase hunger to maintain current body fat levels which in turn leads to the dieting plateau. Once this happens, getting rid of that last bit of body fat is very near impossible.

You will find that when first starting on a new dieting phase that bodyfat is lost quite quickly along with water weight, but as more body fat is lost the body will initiate the starvation response which in turn lowers leptin levels to drop sharply which increases the appetite, and a reduction of energy expenditure. The cheat day will curb the starvation response by tricking the body into thinking that more food is now available and bring the body out of the starvation mode. This will allow a continued loss of body fat over the next few weeks or months.

The increased leptin production brought on by the cheat day elevates the metabolism and keeps hunger at bay for longer periods of time. To get the most effect of the elevated leptin production plenty of carbohydrates are needed particularly the non fibrous carbohydrates such as pasta, rice, bread, potatoes, cereals etc. This is one time that the high glycemic foods that you have been strictly avoiding are the best foods to eat; you can even eat your favorite sugary foods like pastries, biscuits and other glucose laden snacks.

But as mentioned previously above you can “virtually” eat anything that you want, but not in massive amounts. Protein intake should be kept at 1g per pound of body weight; fruit should be kept to a minimum. An increase of calories of 50% of your current dietary intake is the maximum that you should go to as any increase over this amount may increase bodyfat levels. You may find that as fat levels get low that a more regular refeed day is required due to the lower the bodyfat level the more the body will resist further fat loss by further reducing leptin production. In this situation a cheat day may be required every five or six days.

Weight training is very important in increasing and maintaining your muscle mass. The reason why we lose muscle tissue when dieting, even though protein intake is high, is hormonal and the reason why we can’t gain muscle without overeating again is hormonal. And it is leptin that controls these hormones with the exception of insulin. Both insulin and leptin are both affected by glucose. Increased leptin also results in preferential liver glycogen resynthesis; it also increases testosterone levels and increases in growth hormone, and blunts cortisol release.

Method 2: Calorie Cycling

Another method that is used to achieve low levels of body fat and eliminating dieting plateaus is by cycling the intake of calories. Calorie cycling will also keep leptin levels high and again confuse the body into not allowing the normal starvation mode dieting plateau.

This type of dieting requires effort in the planning of food and calorie intakes, but never gives the body chance to get into the starvation mode. There is a limit to the amount of extra calories you can ingest, and should remain at approx 300 more or less calories than the normal daily intake.

An example would be that if your required calorie intake is 2000 calories per day then a 3 day cycle would give; day 1 would be a reduced intake to 1700 calories, day two would mean an increase up normal levels of 2000 calories, and day 3 would be an increase up to 2300 calories. The cycle would then continue for the next three days, day 4; 1700 calories, day 5; 2000 calories, day 6; 2300 calories. The average intake over the three day cycle is still the normal 2000 calories. This cycle would continue until your desired body fat level is reached. When coming off this type of dietary manipulation it is recommended that increase in calories is in small increments only to stop any hormonal reactions.

More information can be found in these articles:

  1. How to construct a bodybuilding diet
  2. Losing fat & cutting without losing muscle
  3. Nutrition ror beginners - part I
  4. Nutrition for beginners - part II

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The Role of Leptin in Regulating Neuroendocrine Function in Humans.
Susan Bluher and Christos Mantzoros
The stimulatory effect of leptin on the neuroenocrine reproductive axis of the monkey. Endocrinology 1998 Nov; 139 (11): 4652-62
Finn PD, Cunningham MJ, Pau KY, Spies HG, Clifton DK, Stiener RA.
Leptin regulates pulsatile luteinizing hormone and growth hormone secretion in the sheep. Endocrinology 200 Nov; 141 (11); 3965-75
Nagatani S, Zeny Y, Keisler DH, Foster DL, Jaff CA.
Evidence that glucose metabolism regulates leptin secretion from cultured rat adipocytes. Endocrinology 1998 Feb; 139 (2): 551-8
Mueller WM, Gregoire Fm, Stanhope Kl, Mobbs CV, Mizuno TM, Warden CH, Stern JS, Havel PJ.
Leptin levels in human and rodent: Measurement of plasma leptin and ob RNA in obese and weight reduced subjects. Nat Med 1995 Nov; 1 (11): 1155-61.

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6 Comments+ Post Comment

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Posted Fri, 04/05/2013 - 18:08

I have lost about 125 pounds with another 25 to go and have been stuck in the same 5 pound range since September. I find this information very interesting and will be testing some of it out. Thanks for posting!

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Posted Sun, 04/22/2012 - 14:20

I understand and am familiar with the concept you are speaking of here. I just don't know how would you explain those with anorexia nervosa are able to lose so much fat and muscle mass. I know their bodies would down regulate their metabolism to preserve necessary energy to maintain basic physiological needs: respiration, cardiac fxn,etc..
I would be interested in your thoughts on this.

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Posted Sun, 04/22/2012 - 05:10

Hello Doug,
How can I contact you apart from comments...Thanks

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Posted Wed, 07/13/2011 - 20:10

very informative! thanks!

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Posted Wed, 08/18/2010 - 03:58


I have read this type of article before on this site and have seen the benifits to "cheat days". My wife has been trying to cut body fat and she always asks me why if she is working out and sticking to her calorie deficit lifestyle/ diet is she staying the same. Now I have a hard copy to show her why.


Anchorage Alaska

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Posted Fri, 03/12/2010 - 19:57
ashley schutz

I like this article because it demonstrates A. that hard work DOES allow a reward at the end of it, and something to look forward to and B. why a Cheat day is important for your body and for fat loss. Great article. I think we should delve more into Set Points and Cheat Days more in articles.