January 24, 2003
Clue For Life Extension By Calorie Restriction Found

Even though the rodents ate more food than normal mice they had less fat and lived longer.

Clever genetic detective work may have pinpointed the reason why a near-starvation diet prolongs the life of many animals.

Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan of mice by 18 per cent by blocking the rodent's accumulation of fat in specific cells. This suggests that leanness - and not necessarily diet - promotes longevity in "calorie restricted" animals.

The experiment was done by knocking out (ie disabling or removing) a gene that codes for the insulin receptor found on fat cells. Without this receptor the fat cells had no way of being told by insulin to pick up sugar from the blood. Hence the fat cells couldn't get the raw materials they needed in order to be able to make and store fat. The consequence was a substantial boost in life expectancy.

As a consequence of this modification, they cut off the fuel supply that enables the body to lay down fat.

These "Firko" (fat-specific insulin receptor knock-out) mice ate normal diets but had reduced fat mass and lived 18 per cent longer on average than normal mice. Even when they were made to overeat, they stayed lean.

While calorie restriction (CR) typically boosts life even more (30% in some cases) this result tends to suggest that one mechanism by which CR works is by reducing the amount of stored fat. Recent research results on the risks of intra-abdominal fat suggests a number of mechanisms by which a reduction in fat will increase life expectancy.

Reducing intra-abdominal, or visceral, fat is important because in addition to increasing the risk of cardiovascular disease and diabetes, among other conditions, such fat can raise insulin levels, which promotes the growth of cancer cells.

People with high levels of intra-abdominal fat may not even know it, McTiernan said, because it is hidden, deposited around the internal organs within the abdomen. "Most women don't know about intra-abdominal fat, but they should, since it is the most clinically significant type of fat and it's where women tend to store fat after menopause."

Although it is known that so-called "apple-shaped" people who store their fat around the stomach are at higher risk for conditions such as diabetes, hypertension and stroke than "pear-shaped" people who store their fat in their buttocks and thighs, visceral obesity is not necessarily correlated with body shape, McTiernan said. The only accurate way to determine the presence and extent of intra-abdominal fat is with imaging procedures such as CT or MRI scans.

Share |      Randall Parker, 2003 January 24 01:36 AM  Aging Reversal


Comments
michael mcglenister said at March 13, 2003 5:05 PM:

Re: Jan 24/03 post. Fat cells do not take up sugar and make fat from it. The liver does that. It then returns the fatty acids to the bloodstream where the fat cells, under the influence of insulin, take in the fat.

The article in the Telegraph also had an improper lead. Jack sprat wasn't lean because he ate no fat. Fat does not cause the secretion of insulin; therefore it does not stimulate fat storage. It is excess carbohydrates that causes the secretion of excess insulin that is necessary for fat storage.

However, while eating excess carbohydrates stimulates fat storage, a double whammy occurs when you eat fat with those excess carbs. This is because the insulin causes the cells to take up ALL the fatty acids in the bloodstream, both those made by the liver and those consumed. If you want to stay lean avoid excess sugar. If you can't control your sweet-tooth then DO NOT EAT FAT AND SUGAR AT THE SAME TIME unless the quantity is very small. In other words: avoid cakes, cookies, pies, etc.

Protein acts the opposite of insulin. It causes the secretion of glucagon which opens up the fat cells. So, to be lean: avoid excess carbs, avoid fat and sugar combos. It follows that if you are restricting carbs and maintaining current fat consumption levels you must necessarily increase your protein consumption to maintain calorie levels.

This is the secret to being lean.

sincerely,

M. McGlenister

mikepowers said at August 17, 2003 4:01 PM:

From personal eating habits it should be clear
that we don't crave pure sugar (starch is a concentrated sugar) or pure fat.

Who craves to eat a bowl of pure sugar or honey?
Who craves a plain baked potato?
Who craves to eat a bar of pure butter or drink
olive oil from the bottle?

The answer is no one.

What we crave are fat/carbohydrate combinations.

Needless to say, such combinations are strickly
man made.

Perhaps the reason why we crave this [unnatural] fat/carbohydrate combination, is that the body
registers its fat promoting power.

Under natural circumstances laying down a layer
of fat is good - it allows us the capacity to
fast when food is not available.

However, in the modern world food is normally
always available.

So we have a problem here.

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