THE POWERFUL ROLE OF LEPTIN
Leptin tells the brain when we need food, how much to have and when to stop eating. It also does other things including increasing energy, regulating blood circulation, preventing blood clots, and regulating body temperature and reproduction.
Leptin is produced by body fat, and signals the brain to let us know when we are hungry or full. A low leptin level signals the brain to eat more. A high leptin level tells it to stop eating by suppressing appetite. This hormone also tells our body where to store excess fat. People who are leptin resistant typically gain weight in the belly – the most unhealthy kind of fat.
‘Fasting’ leptin (measured first thing in the morning) should be low. If it’s high, it is probably because the body is de-sensitised to leptin, known as leptin resistance. High fasting leptin indicates that the body will ‘sabotage’ any weight loss efforts that we are making and also open the way for a cascade of health problems.
Besides obesity, abnormally high leptin levels greatly increase the risk of heart disease, diabetes, osteoporosis, arthritis, autoimmune diseases, reproductive disorders and premature ageing. Inflammatory diseases are strongly promoted by high leptin levels. Leptin is much more important to heart health than cholesterol, yet very few practitioners know this.
The following study found that leptin resistance accompanied by a high-fat and high-calorie diet results in weight gain and obesity.
The Key Trouble Maker, Fructose
Researchers of the American Physiological Society showed in 2008 that high levels of fructose can slowly cause leptin to cease functioning properly. For six months, they fed one group of rats a high-fructose diet and another group, the control group, a fructose-free diet. At the end of the period, the only difference between the groups was that the high-fructose-diet group developed higher triglyceride (blood fat) levels. [Note that the Natural Health Society is opposed to research involving animals. However, as this research has been done, we may as well see the results.]
At the end of the six months, both groups of rats were injected with leptin to see how the animals' eating behaviour responded. Higher levels of leptin should have caused the rats to eat less food, and the fructose-free rats did consume less. But the rats that had consumed high fructose did not reduce their intake. The searchers concluded that high levels of fructose suppress the action of leptin.
Next the researchers put both groups of rats on a high-fat, high-calorie diet of the kind many Americans eat. They found that the high-fructose rats which were leptin resistant ate more and gained much more weight and fat than the fructose-free control group.
This was the first study to demonstrate that leptin resistance can be brought on by high fructose consumption.
All told, this study showed that leptin resistance can:
- develop by eating a lot of fructose;
- develop silently, that is, with no outward indication it is happening;
- result in weight gain when the diet is high fat and high calorie.
One of the researchers commented, "This study may explain how the global increase in fructose consumption is related to the current obesity epidemic."
How Fructose Works
Why does fructose suppress leptin? Studies have found that elevated blood triglycerides tend to prevent leptin crossing the blood-brain barrier. Because fructose raises triglycerides, it would indirectly prevent leptin from reaching the brain, and if leptin does not reach the brain, the brain will not signal that it is time to stop eating.
It has been discovered that fructose in the liver does three things that are particularly harmful – it promotes uric acid production, it initiates fat production in the liver, and it promotes an enzyme called Junk One.
Junk One has been shown by
Fructose in Abundance
Fructose is the prominent sugar found in fruit, but it's not the normal consumption of fruit that is the problem. Refined sugar and high-fructose corn syrup (made from corn starch) are both about 50% fructose, and these ingredients have become increasingly common in many foods and beverages. People are now consuming much more fructose than ever before.
Average consumption of fructose from refined sugar and fruit juices by Australians has gone from almost nil a century ago to around 22.5 kilograms per person per year (60 grams per day) in year 2000. Unfortunately for Americans, they consume one-and-a-half times this amount.
At these levels, fructose is toxic to the liver. It's not that the calories in fructose are different, it's the fact that the only organ in the body that can take up fructose is the liver. High fructose also raises blood sugar and insulin, both of which affect the regulation of hunger.
By adding fructose for the reason that it doesn’t depend on insulin, food manufacturers may be fuelling the obesity epidemic – in addition to causing liver damage.
Medications for Leptin Resistance
New medications for type-2 diabetes, Byetta and Symlin, are being used for leptin resistance treatment, and producing dramatic weight loss in people who are leptin resistant. The drawback is that there are negative side effects.
A more natural leptin resistance treatment uses an extract from the African plant, Irvingia Gabonensis. This herb alone can help correct leptin resistance.
The Right Foods Could Do It Best
A diet high-ish in good fats has been found to be successful for leptin resistance. Good fats are monounsaturated fats as in olive oil, canola oil, avocados, nuts, seeds, olives and dark chocolate.
On the other hand, the worst way of eating if there is leptin resistance is a diet overloaded with carbohydrates and saturated fats. High carbohydrate foods are breads, pasta, breakfast cereals, rice, cakes and other grain foods. All concentrated and refined sugars and other junk foods should be avoided. Even a high-carbohydrate diet that is low in fat has been found to be not effective in getting rid of belly fat and reducing overall weight.
A Vicious Cycle
Many investigators have shown that high-fructose eating day after day for years causes the body to become insulin resistant, so that it then makes even more insulin.
The fructose-leptin-insulin mechanism was summarised on ABC Radio National on 9th July 2007 by Dr Robert Lustig, Professor of Paediatric Endocrinology at the
“Putting all this together, there is a cycle of increased insulin causing increased production of liver fat, liver deposition of fat, increased inflammation, non-alcoholic fatty liver disease and inability of the brain to recognise leptin. You then consume more fructose, produce a whole lot more insulin, and so on, and now there is a vicious cycle out of control.
“Fructose – because of the way it's metabolised – is actually damaging the liver in the same way as does alcohol. It's like alcohol without the buzz!”
THE DIRECT ROLE OF INSULIN IN OBESITY
Researchers have found that people with high levels of insulin find it much more difficult to lose weight than people with low levels. This is to do with impaired sensitivity of the insulin-receptors on bodily cells.
When these receptors are desensitised, the body attempts to correct this by making more insulin. One of the effects of insulin is to inhibit a fat-burning hormone called hormone-sensitive lipase, a hormone which releases fat into the bloodstream to be used for fuel. But if this enzyme is inhibited by high insulin, the body can’t burn fat, so it will burn carbohydrates and protein (from muscles) for energy.
The aim is to have low levels of insulin so that large amounts of hormone-sensitive lipase will be produced, and the body will burn fat throughout the day and get rid of those excessive deposits.
Putting this another way, by focussing on getting insulin levels down – rather than focussing on calorie intake – the fuel being consumed will be burned by muscle rather than being forced to be stored as fat.
It has been observed that when insulin levels come down from high levels, obese people (who had no other health problems) greatly reduced their carbohydrate intake. They stopped snacking between meals and stopped drinking soft drinks – without even being told to do so. Because they felt better, they began regular exercise and they lost weight. They continued eating less and exercising, and kept losing weight.
The key point is that insulin receptors on bodily cells stop working properly when people eat a lot of junk foods and/or when they don’t have the regular physical activity for which the body is designed.
Along with avoiding junk foods, regular exercise will lower insulin, especially if it is strength training that builds muscles. In fact, exercise is the best ‘treatment’ for high insulin by far.
It is a well established fact that exercise is a key to overcoming obesity, and people naturally assume that this is because it burns calories. But this idea is unrealistic because 20 minutes of jogging burns only the calories in just one choc-chip cookie.
Exercise certainly does burn calories, but it also does three other things that have more potent effects:
- It increases insulin sensitivity in skeletal muscle, causing insulin to work more effectively.
- It reduces cortisol levels. Cortisol is a stress hormone that also causes deposition of abdominal fat, leading to a ‘gut’.
- It helps to counter the effects of fructose.
Abnormally high leptin indicates that the body is de-sensitised to leptin. This leptin resistance can be brought on by high fructose consumption, and if the diet is high in saturated fat and calories, the result will very likely be weight gain.
High fructose eating also promotes and enzyme called Junk One which causes insulin levels in the bloodstream to rise. High insulin causes more fat to be made.
The fructose in whole fruit is not the problem. It is the fructose contained in large amounts of refined sugar, fruit juices and high-fructose corn syrup that do the damage.
The worst way of eating if there is leptin resistance is a diet overloaded with carbohydrates (refined sugar, bread, pasta, breakfast cereal, rice and cakes) and saturated fats. Good fats (to have in moderation) are those in avocados, nuts, seeds, olives and olive oil. Following Natural Health Dietary Guidelines should restore normal appetite regulation.
Double benefits come from regular exercise. It causes insulin to work more effectively, lowering its levels, and helps to counter the effects of fructose.