Breakfast is a Dangerous Meal: Why You Should Ditch Your Morning Meal For Health and Wellbeing. Terence Kealey

Чтение книги онлайн.

       Why do dieters return to their previous weight?

      Just as Mark Twain is reported to have said that quitting smoking was easy, he’d done it a thousand times, so dieters find it equally easy to lose weight, they’ve done it a thousand times. But then they put it back on again, and repeated studies have confirmed that 80–90 per cent of dieters revert to their previous weight.⁶ At least five reasons have been proffered for this yo-yo dieting: namely (i) pleasure, (ii) the replacement of muscle by fat, (iii) resetting the basal metabolic and exercise rates, (iv) hormones and (v) genes.

      Pleasure: Conventional dieting is rarely fun, and the temptation to start eating again at the end of a weight-loss diet is strong, so people who skipped breakfast when dieting will, on breaking their diet, eat it again (thus, incidentally, creating the paradox of large people skipping breakfast and slim ones eating it).

      The replacement of muscle by fat: Dieters do not lose only fat: many researchers report that dieters, on losing weight, lose muscle mass as well. But on recovering their weight, former dieters put back more fat than muscle. And because fat consumes less energy than muscle, the former dieter – if they want to maintain a fixed weight – needs to eat less food than before, which they will generally fail to do.

      The first study to report this so-called ‘preferential restocking of fat tissue on refeeding’ was the famous Minnesota starvation study that the now notorious (see later) Ancel Keys performed over 1944/45. Concerned by the mass starvations of the Second World War, and believing (rightly) that they needed to be better understood, Keys recruited thirty-six conscientious objectors (male, lean, aged 22–33) with his celebrated advert, ‘Will you starve that they be better fed?’ He then indeed starved – and re-fed – his volunteers, and in his classic 1950 book The Biology of Starvation he reported the preferential restocking of fat tissue on re-feeding. And though not all researchers, on repeating Keys’s experiment, find the preferential restocking,⁷ most do:⁸ for once Keys told it like it probably is. Only if dieters consume a reasonable amount of protein – and take exercise – will they help sustain muscle mass.⁹ My wife tells me, by the way, that this knowledge is widely known by personal trainers.

      Resetting the metabolic and exercise rates: The Biggest Loser is an American reality television show where people compete to lose weight. Some people achieve massive weight loss (Danny Cahill, who is now 46, from Season 8, lost 239 pounds – 17 stones or 108 kg – in seven months) but, as the New York Times ran on its front page for 2 May 2016, these contestants then hit the problem of ‘adaptive thermogenesis’ (from the Greek therme, ‘heat’, and gignesthai, ‘to be born’), which is a posh way of saying that human bodies will vary the amount of energy they use.

      To be anthropomorphic, our bodies do not want to lose weight: our bodies are programmed by evolution to see starvation as a terrible threat, so a body that has experienced significant weight loss will, in a response that is sometimes known as the Survival of the Fattest, save energy by decreasing its metabolic rate. And that decrease may apparently be permanent. Nor are we talking small differences: in the words of an influential study: ‘A formerly obese individual will require about 300–400 fewer calories per day to maintain the same body weight and physical activity level as a never-obese individual of the same body weight and composition.’¹⁰

      The Biggest Loser research study from the National Institutes of Health, on which the New York Times based its story, found that the figure was higher, around 600 calories a day.¹¹ This number of calories is almost the size of a meal, and someone who’s dieted will have to skip it permanently if they’re to maintain the same weight as someone who’s never dieted. Danny Cahill, for example, failed to do so, and he’s now 104 pounds (7 stones 6 pounds, or 47 kg) heavier than he was seven years earlier.

      Although some studies fail to find adaptive thermogenesis in dieters (which in the interests of balance I note here)¹², the majority do, and so we see how adaptive thermogenesis fights dieters. And, actually, it does so not only by slowing down their rate of metabolism but also by reducing the intensity of a phenomenon that is not widely recognised, namely casual exercise.

      Physical activity can be monitored by portable meters or ‘accelerometers’ (the precursors of activity trackers such as Fitbits and Jawbones) and it transpires that dieters and post-dieters engage in less casual activity than their non-dieted peers: so dieters and post-dieters might take a lift rather than climb the stairs, or they might fidget less or drive short distances where once they would have walked.¹³ Dieters and post-dieters seem, therefore, to lose the spontaneous impulse they once had to climb stairs or stretch their legs.

      Adaptive thermogenesis thus offers another explanation for the paradox of breakfast skippers consuming few calories while being large: breakfast skippers will often be yo-yo dieters who (1) because of adaptive thermogenesis will burn relatively few calories, yet who (2) because of the yo-yo will be large. But it wasn’t the breakfast skipping that enlarged these people, it was the yo-yo dieting-induced adaptive thermogenesis.

      Hormones: Our hormones also don’t want us to lose weight; a research group from Melbourne, Australia, found that overweight or obese subjects, on losing a significant amount of weight, demonstrate – even a year after the diet has stopped – higher levels of hormones such as ghrelin (which increases hunger) and lower levels of hormones such as leptin (which decreases hunger).¹⁴

      Genes: Is our weight determined by our genes or our environment? Professor Tim Spector, the twin expert from King’s College London, has found that: ‘on average identical adult twins are less than 1 kg different in weight.’¹⁵

      Genetics, in short, play a huge role (about two-thirds of the influence) in setting a person’s weight,^fn1 and only about a third of the influence is due to the environment.¹⁶ If we diet, therefore, in Professor Spector’s words: ‘Our bodies simply seem to adapt to the reduced calorie intake and do what they are programmed by evolution to do … This is why most diets fail.’¹⁷

      Worryingly, weight-loss dieting might even induce weight gain. In 2012 a research group from Finland reported on identical twins where one of the twins had deliberately lost at least 5 kg (11 pounds, ¾ stone) on at least one occasion but where the other twin had never gone on a diet. And the dieters had eventually ended up, on average, 0.4 kg (1 pound) heavier than the non-dieters.¹⁸

      Conclusion: A group from Switzerland, on reviewing the field, has concluded that slim people should never diet: they risk eventually putting on weight. Only large people should diet: only for them might it lead to weight loss.¹⁹

      Dieting being unexpectedly problematic, we need to identify a strategy – a lifestyle – that allows people to lose weight and to keep it off. As we shall see, skipping breakfast will help achieve that.

       8

СКАЧАТЬ