However, modern obesity research disagrees… and scientists are increasingly pointing their fingers at a hormone called leptin.
Leptin and Leptin Resistance: Everything You Need to Know
Leptin is a hormone that is produced by the body’s fat cells.It is often referred to as the “satiety hormone” or the “starvation hormone.”
It also has many other functions related to fertility, immunity, brain function and others.
The leptin system evolved to keep us from starving or overeating, both of which would have made us less likely to survive in the natural environment.
These days, leptin is very effective at keeping us from starving. But something is broken in the mechanism that is supposed to prevent us from overeating.
Leptin is Supposed to Tell The Brain That We Don’t Need to Eat
The way leptin works is relatively simple…This hormone is produced by the body’s fat cells. The more body fat they carry, the more leptin they produce.
Leptin is carried by the bloodstream and into the brain, where it sends a signal to the hypothalamus… the brain area that controls when and how much we eat.
The fat cells use leptin to “tell” the brain how much body fat they carry. Lots of leptin tells the brain that we have plenty of fat stored, while low levels of leptin tell the brain that fat stores are low and that we are at risk of starvation.
This schematic shows how leptin is supposed to work:
We eat –> body fat goes up –> leptin goes up –> we eat less and burn more.
Or…
We don’t eat –> body fat goes down –> leptin goes down –> we eat more and burn less.
This kind of system is known as a negative feedback loop and is similar to the control mechanisms for many different physiological functions… such as breathing, body temperature, blood pressure and others.
Leptin Resistance May be The Main Biological Abnormality in Obesity
People who are obese have a lot of body fat in their fat cells.Because fat cells produce leptin in proportion to their size, obese people also have very high levels of leptin.
However… the problem is that the leptin signal isn’t working. There’s a whole ton of leptin floating around, but the brain doesn’t “see” that it is there.
When the brain doesn’t receive the leptin signal, it erroneously thinks that the body is starving, even though it has more than enough energy stored.
- Eating More: The brain thinks that we MUST eat so that we don’t starve to death.
- Reduced Energy Expenditure: The brain thinks we need to conserve energy, so it makes us feel lazier and makes us burn fewer calories at rest.
For the great majority of people, trying to exert cognitive inhibition (willpower) over the leptin-driven starvation signal is next to impossible.
Losing Weight Reduces Leptin, so The Brain Tries to Gain The Weight Back
Most “diets” don’t provide good long-term results. This is a well known problem in weight loss studies.Diets are so ineffective that whenever someone goes from obese to thin, it is seen as newsworthy material.
The truth is… when it comes to losing weight, long-term success is the exception, NOT the rule.
There are many possible reasons for this, but the research is showing that leptin may have a lot to do with it.
Losing weight reduces fat mass, which leads to a significant reduction in leptin levels, but the brain doesn’t necessarily reverse its leptin resistance.
When leptin goes down, this leads to hunger, increased appetite, reduced motivation to exercise and decreased amount of calories burned at rest.
Basically, the reduced leptin makes the brain think it is starving… so it initiates all sorts of powerful mechanisms to regain that lost body fat, erroneously thinking that it is protecting us from starvation.
This is the main reason so many people “yo-yo” diet… they lose a significant amount of weight, only to gain it back (and then some).
What Causes Leptin Resistance?
According to Dr. Guyenet, several cellular mechanisms behind leptin resistance have been identified.- Inflammation: Inflammatory signalling in the hypothalamus is likely an important cause of leptin resistance in both animals and humans.
- Free Fatty Acids: Having elevated free fatty acids in the bloodstream may increase fat metabolites in the brain and interfere with leptin signalling.
- Having high leptin: Having elevated levels of leptin in the first place seems to cause leptin resistance.
What Science Knows About Reversing Leptin Resistance
The best way to know if you are leptin resistant, is to look in the mirror.If you have a lot of body fat, especially in the belly area, then you are almost certainly leptin resistant.
- Avoid processed food: Highly processed foods may compromise the integrity of the gut and drive inflammation.
- Eat Soluble Fiber: Eating soluble fiber can help improve gut health and may protect against obesity.
- Exercise: Physical activity may help to reverse leptin resistance.
- Sleep: Poor sleep has been implicated in problems with leptin.
- Lower your triglycerides: Having high blood triglycerides can prevent the transport of leptin from blood and into the brain. The best way to lower triglycerides is to reduce carbohydrate intake.
- Eat Protein: Eating plenty of protein can cause automatic weight loss. There are many reason for that, one of them may be an improvement in leptin sensitivity.
Take Home Message
Obesity is not caused by greed, laziness or a lack of willpower.Not because this diet turns people into gluttons and sloths, but because it alters our biology in a way that changes our behavior.
Leptin is the “master hormone” of body fat regulation.