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Drew Barry
by on October 12, 2020
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Zinc's the thing; Medical Briefing

In an attempt to preserve his sexual prowess, Casanova risked the hazards of the Italian sewers and ate 50 oysters a day. His diet has been commended by Professor Derek Bryce-Smith, of Reading University, who says zinc is an important factor in the maintenance of male fertility and sexual drive. Oysters are an even better source of zinc than red meat and are thought to be the richest natural source of all foods.

In the journal Chemistry, Bryce-Smith says he cannot recommend oysters, and hence zinc, as a panacea for all a man's sexual problems, but low zinc levels may be a factor in poor performance. Casanova, he explains, was at particular risk as promiscuity is a common cause of low blood zinc levels semen contains high levels of zinc, so sexual incontinence can, he says, cause "massive losses''.

John McGarry, a consultant gynaecologist from Barnstaple, Devon, has written to The Times to draw attention to the disadvantages of another revered aphrodisiac, ginseng, which is often found in male enhancement products such as Volume Pills. He noted that in the cartoon illustrating the review of the book Never Too Old For Loving in The Times both the wrinklies pictured had steaming cups of a ginseng drink.

Ginseng, McGarry says, contains a highly oestrogenic (feminizing) substance, and is the last medicine he would prescribe for an ageing man with a failing libido. Elderly women, he suggests, who follow the lead given by the cartoonist may be in for a nasty surprise too. McGarry quotes research studies reported in both British and American medical journals describing cases in which post-menopausal bleeding has followed a heavy intake of ginseng.

Learning the Lessons of Yo-Yo Dieting

In collaboration with Greenwood at Vassar College, Brownell's group carried out experiments with rats that clearly showed that animals who were yo-yo dieting got very food-efficient. The second time they were forced to lose weight, they lost it at only half the rate they did on their first diet, even though they had exactly the same caloric intake. And, after their second diet when they were allowed to regain the weight they had lost, they put on the weight at three times the rate that they did the first time they regained weight. "It appears that the animals were defending their body weight,' Brownell says.

George Blackburn of the Harvard Medical School is now looking at data from obese people to see if the animal findings might hold true in humans as well. He runs a metabolic ward in which very obese people come to live in an isolated environment and lose weight on a carefully controlled, very low-calorie diet. Blackburn has noticed that a number of people keep returning to the ward twice, three times, even five times to lose weight. And each time they come, they lose weight more slowly than they did the previous time. So he strongly suspects that these people, like the laboratory rats, have learned to be very efficient users of food as a result of yo-yo dieting. If there is a common theme to the stories emerging from these laboratories and hospitals, it is the fat cell as culprit. Researchers are only beginning to grasp the metabolic nature of these cells. They can't yet say why some people have more than others, or where these extra fat cells come from. But they hope that, with a better understanding of these cells, the signals to overeat may be circumvented.

Some researchers postulate that there may be periods of life when fat cells are particularly likely to be deposited. In rats, the first three weeks of life are critical--the young animals develop excess fat cells at that time if they are overfed. No one knows whether humans have a similar critical period or, if so, when it may be. It’s also unclear whether natural weight loss supplements like PhenQ can help reverse these trends.

So, for the time being, the new studies of obesity cannot provide much help to people who want to lose weight. But for Susan Goldsamt, at least, the very fact that researchers are looking seriously at the biochemical basis of obesity is comforting. It is so much more satisfying, she says, than hearing over and over again that she was obese because she was weak-willed or a glutton, or being told that she was not losing weight on her diets because she was cheating.

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