ISLAMABAD – After all the hype over a low calorie diet being the tried and tested way to shed unwanted pounds or adding years to your life, comes the disappointing news — it doesn’t add to your longevity.
“If there’s a way to manipulate the human diet to let us live longer, we haven’t figured it out yet and it may not exist,” said biologist Steven Austad from the University of Texas Health Science Centre, who conducted the analysis.
Since 1934, research has shown that lab rats, mice, yeast, fruit flies and round worms fed 10 percent to 40 percent fewer calories than their free-eating peers lived some 30 percent longer. In some studies, they lived twice as long, the journal Nature reported.
Such findings have spawned a growing community of believers who seek better health and longer life in calorie-restricted (CR) diets, as promised in the 2005 book “The Longevity Diet,” including 5,000 members of the CR Society International, according to the Daily Mail.
The research has also prompted companies like Procter & Gamble and Nu Skin Enterprises to develop drugs to mimic the effects of calorie restriction.
The new study, from the National Institute on Aging (NIA), part of the US National Institutes of Health, suggests this link doesn’t hold true for all species.
It found that most of the 57 calorie-restricted monkeys did have healthier hearts and immune systems and lower rates of diabetes, cancer or other ills than the 64 control monkeys. However, there was no longevity pay-off.
“You can argue that the calorie-restricted animals are healthier,” said Austad.
“They have better cholesterol profiles, less muscle loss, less disease. But it didn’t translate into greater longevity. What we learn from this is you can un-link health and longevity,” added Austad.
The NIA study, launched in 1987, is one of two investigating whether eating just 70 percent of the calories in a standard lab diet extends life in a long-lived primate.
The Wisconsin National Primate Research Centre’s study, begun in 1989, also uses rhesus monkeys, whose physiology, genetics and median lifespan (27 years) are closer to humans than are the rodents in earlier calorie-restriction research.
Babies diet determines risk of obesity
Baby rats, which get normal levels of dietary fat right after birth, even though their mothers were fed high-fat diets, avoid obesity and related disorders as adults, according to new research.
Conversely, rat babies exposed to a normal-fat diet in the womb but nursed by rat mothers on high-fat diets become obese by the time they are weaned.
The experiments suggest that what mammalian babies - including humans - get to eat as newborns and young children may be more important to their metabolic future than exposure to unhealthy nutrition in the womb, Johns Hopkins scientists say, the journal “Diabetes” reports. “Our research confirms that exposure to a high-fat diet right after birth has significant consequences for obesity,” says Kellie L.K. Tamashiro, assistant professor of psychiatry and behavioural sciences at the Johns Hopkins University School of Medicine, who led the study.
“But it also suggests that by putting children on a healthy diet in infancy and early childhood, we can intervene and potentially prevent a future of obesity, diabetes and heart disease,” adds Tamashiro, according to a Johns Hopkins statement.
Obesity has become a worldwide public health problem that often leads to many other disorders, such as cardiovascular disease, hypertension, type 2 diabetes, some cancers and arthritis.
Newborn baby rats exposed to a high-fat diet through the breast milk of rat mothers fed high amounts of fat were more likely to gain excessive weight, have impaired tolerance to glucose (a sign of pre-diabetes) and become insensitive to the hormone leptin, which regulates appetite and body weight in humans and rodents and can be disrupted in obese mammals.
Leptin, secreted by fat cells, signals how much fat is around and controls food intake; obese people often are insensitive to the signals, for reasons so far unclear.
Latest scan can tell need for bypass
An ultra-fast, 320-detector computed tomography (CT) scanner can tell, which people with chest pain need or do not need cardiac angioplasty or bypass surgery to restore blood flow to the heart.
“The CORE 320 study is the first prospective, multi-centre study to examine the diagnostic accuracy of CT for assessing blockages in blood vessels and determining which of those them may be preventing the heart from getting adequate blood flow,” says Joao A.C. Lima, senior study author and professor of medicine and radiology at Johns Hopkins University School of Medicine.
“We found an excellent correlation in results when we compared the 320-detector CT testing with the traditional means of assessment using a stress test with imaging and cardiac catheterisation,” says Lima, according to a Johns Hopkins study. The findings, says Lima, will apply to people who have chest pain but are not having a heart attack.
Many people in that situation are sent to a cardiac catheterisation lab for further evaluation with angiography, an invasive test to look for blockages in the coronary arteries using dye and special X-rays.
About 30 percent of people who have such catheterisation are found to have minimal disease or no blockage requiring an intervention to open or bypass the vessel.
Lima says a nuclear medicine stress test with imaging, known as SPECT, shows reduced blood flow to the heart without indicating the number or specific location of blockages.
The 381 patients who completed the study had traditional SPECT tests and invasive angiography.
They also had two types of tests with a non-invasive 320-detector CT scanner.
In the first CT test, the scanner was used to see the anatomy of vessels to assess whether and where there were blockages. That test is known as CTA, in which the ‘A’ stands for angiography.
Then, in a second CT test with the same machine, patients were given a vasodilator, a medicine that dilates blood vessels and increases blood flow to the heart in ways similar to what happens during a stress test.
The second test is called CTP, with the ‘P’ standing for perfusion. Carlos E Rochitte, cardiologist at the Instituto do Coracao in Sao Paulo, Brazil, who led the study, said: “We found that the 320-detector CT scanner allowed us to see the anatomy of the blockages as well as determine whether the blockages were causing a lack of perfusion to the heart.”
The 320-detector CT provides a complete picture of the heart by making just one revolution around the body.
The researchers say the two tests combined - CTA and CTP - still produce less radiation than a scan with the 64-detector in widespread use today.
Results of the study were presented at the European Society of Cardiology Congress in Munich in Germany.