Friday, January 04, 2013

Lustig fructose

"Lustig" is German for "funny" or "amusing".  Usually Ashkenazi  when used as a surname

Robert Lustig is an attention-seeking food-fanatic and seems to be some kind of nut.  But a small recent study suggests that he may be on to something. 

His extreme claims about natural fruit sugar (fructose) being a "poison" have rightly put most of the medical research fraternity against him and the research evidence  against his demonization of fructose is strong.  There are even some studies (e.g. here) that suggest that fructose is good for you.

He does seem to have crumpled under the weight of opposition  and now demonizes sugar generally, including ordinary table sugar, which is a combination of fructose and glucose.  And, broadly speaking, his argument that in some way we get used to a high sugar intake and thus consume more sugar that we otherwise would is reasonable enough.  Habituation is a well-known process in many things.  I reproduce below some comments on his latest book.

But has he given up too soon?  A recent study does show a strong differential response to fructose versus glucose.  Admittedly the study is small and very short term but it is carefully constructed, cautiously analysed and relies on direct brain measurements rather than subjective judgments.

On the other hand (you almost need to be an octopus in this matter) measuring cerebral blood flow is a pretty crude measurement of anything -- but on yet another hand several different measures produced similar results

What I think the latest results suggest is that there needs to be more attention to glucose.  Fructose may not be the villain but glucose may be the saviour!  Lustig may have been right in separating out different types of sugar, even if he originally focused on the wrong one.  Should we replace ordinary table sugar with glucose only?

Glucose is not as sweet as table sugar so we would have to use more of it  -- which might not be good.  But we could add a bit of aspartame for more sweetness.  Yes:  I know the cannonade of condemnation that will greet me from the aspartame freaks.  Been there.  Done that.


Waistband feeling a bit tighter, or buttons straining after Christmas?

While it’s easy to blame your appalling willpower or TV-inspired lethargy, according to a respected U.S. obesity expert, weight gain might not be your fault at all.

In a fascinating new book, Robert Lustig, a professor of clinical paediatrics at the University of California, expounds a whole new scientific theory.

He argues that the urge to overeat and lounge around doing nothing is not a sign of weakness.

It is, he says, a hormonal issue, triggered by eating too much sugar.

He points the finger of blame at the hormone leptin, which acts like an appetite thermostat.

As one of two ‘hunger hormones’ in the body, leptin works to decrease the appetite (its partner, ghrelin, increases appetite).

When you have had enough to eat, your fat cells release leptin, which effectively dulls the appetite by instructing the brain that it’s time to stop eating.

But Professor Lustig warns that our sweet tooth is sending this process haywire.

For many years scientists thought obesity could be caused by a shortage of leptin — thinking that without adequate levels, overweight people simply never received the message that they were full.

But more recent studies have shown that obese people have plenty of leptin (in fact, the fatter you are, the more of it you appear to have), but are more likely to be ‘leptin-resistant’.

This means the cells in the brain that should register leptin no longer ‘read’ the signals saying the body is full, but instead assume it is starving — no matter how much food you continue to eat.

In panic, the brain pumps out instructions to increase energy storage — instigating powerful cravings for high-fat, high-sugar foods because these are the easiest and most immediate forms of energy — and conserve energy usage, by dampening any urge to get up off the sofa and go for a run.

The food cravings are made even more intense — and impossible to resist — because leptin is supposed to dampen the feeling of pleasure and enjoyment you get from food by suppressing the release of the brain chemical dopamine, helping to decrease appetite.

But if you are leptin-resistant, food never stops tasting delicious, no matter how much of it you eat.

This, says Professor Lustig, is why many overweight people find it so hard to stop eating, and why diets so often fail.

Scientists have been struggling to work out what causes leptin resistance.

But now Professor Lustig and his team have been able to show — in repeated studies on humans — that too much sugar in the diet is to blame.

High sugar diets lead to spikes in the hormone.  This is needed to clear sugar out of the blood and into storage as fat.

But repeated insulin spikes, due to a high sugar diet, can lead to a condition called ‘insulin resistance’ (when the cells have been so bombarded by insulin they no longer respond to it).

Professor Lustig believes insulin resistance triggers leptin resistance, and, crucially, he has discovered that by reducing insulin levels it is possible to improve ‘leptin signalling’ (the brain’s ability to read leptin), stop cravings, put the brakes on food consumption — and trigger weight loss.

In his new book Fat Chance, Professor Lustig explains that leptin resistance — and sugar — is at the root of the obesity epidemic.

More here

Dreading your diet? Don't worry...plump people live LONGER than their skinnier counterparts

This cannot be noted often enough

If your New Year’s resolution is to live a healthier life, it might be best to ditch that diet and enjoy another helping of festive leftovers.  For a bit of extra weight could actually help you live longer, according to extensive research.

Men and women who are slightly plump have longer lives than those who are slimmer, it found.

Analysis of the results of almost 100 studies revealed that those who were of normal weight – a usual barometer of health – were likely to die sooner than those who were slightly overweight.

However, those who were any bigger than this were around a third more likely to die during the months or years they were being studied than those of normal weight.

The analysis is not the first to suggest that a bit of extra weight is actually good for health.

Explanations as to why this might be include the possibility that those who start out slightly heavier will have more fat reserves to call on should they lose weight due to ill health as they get older.

It is also possible that concerns about the health of the overweight and obese means that problems linked to weight, such as high blood pressure and diabetes, are more likely to be spotted and treated, improving that person’s overall health.

It has also been suggested that some people’s genes may help them escape the health consequences of being slightly overweight, while a bit of extra padding could help the elderly to survive falls unscathed.

Another theory is that some of those who are overweight may actually exercise more and eat better than thin people who  starve themselves or smoke to suppress  their appetite.

For the latest study, US government researchers read 91 previous research papers  on the topic from around the world – involving millions of men and women.

They looked at the subjects’ body mass index at the start of the research and how likely they were to have died by the end of it.

Body mass index, or BMI, is a mathematical formula relating height to weight.

People are classified as being of normal weight if they have a BMI of between 18.5 and 24.9 and overweight if their reading is between 25 and 29.9.  A BMI higher than this is classified as obese and the bigger the reading the greater the risks to health are thought to be.

The results, published in the Journal of the American Medical Association, showed that those judged to be overweight were 6 per cent less likely to have died by the end of the study period than those of normal weight.

Having a BMI of between 30 and 34.9, and so being slightly obese, also did not seem to harm health.

However, those whose BMI was greater than this were 29 per cent less likely to live to see the end of the study than those whose weight was classed as ‘normal’.


1 comment:

Nuckluck said...

Why should anyone but the terminally dumb find it surprising that conditions the body works hard to create would be bad for it. The normal human or animal body wants to have a protective reserve of fat to tide the body over during any kind of medical crisis yet the foolish decided that all fat is bad and set up "ideal" weights to eliminate all the fat.