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Sunday 30 August 2015

Gary Taubes: Diet Advice That Ignores Hunger

TOWARD the end of the Second World War, researchers at the University of Minnesota began a legendary experiment on the psychology and physiology of human starvation — and, thus, on hunger. The subjects were 36 conscientious objectors, some lean, some not. For 24 weeks, these men were semi-starved, fed not quite 1,600 calories a day of foods chosen to represent the fare of European famine areas: “whole-wheat bread, potatoes, cereals and considerable amounts of turnips and cabbage” with “token amounts” of meat and dairy.

As diets go, it was what nutritionists today would consider a low-calorie, and very low-fat diet, with only 17 percent of calories coming from fat.

What happened to these men is a lesson in our ability to deal with caloric deprivation, which means, as well, a lesson in any expectations we might have about most current weight-loss advice, and perhaps particularly the kind that begins with “eat less” and “restrict fat.”

The men lost an average of a pound of body fat a week over the first 12 weeks, but averaged only a quarter-pound per week over the next 12, despite the continued deprivation. And this was not their only physiological reaction. Their extremities swelled; their hair fell out; wounds healed slowly. They felt continually cold; their metabolism slowed.

More troubling were the psychological effects. The men became depressed, lethargic and irritable. They threw tantrums. They lost their libido. They thought obsessively about food, day and night. The Minnesota researchers called this “semi-starvation neurosis.” Four developed “character neurosis.” Two had breakdowns, one with “weeping, talk of suicide and threats of violence.” He was committed to the psychiatric ward. The “personality deterioration” of the other “culminated in two attempts at self-mutilation.” He nearly detached the tip of one finger and later chopped off three with an ax.

When the period of imposed starvation ended, the subjects were allowed to “refeed.” At first they were allowed to eat more calories, but restricted as to how much. A subset under continued observation was then allowed to eat to satiety, which was surprisingly hard to achieve. The men consumed prodigious amounts of food, up to 10,000 calories a day. They regained weight and fat with remarkable rapidity. After 20 weeks of recovery, they averaged 50 percent more body fat than they had when it began — “post-starvation obesity,” the researchers called it.

Implicit in many discussions of how best to lose weight is the assumption that hunger, which is a consequence of caloric deprivation, is not an issue. Health and government organizations tell the obese and overweight, who now make up just over two-thirds of our adult population, to do what the study’s subjects did: Eat less, cut back on calories.

That advice implies that the ensuing hunger will be an easily bearable burden (no depression, lethargy, irritability — no tantrums, please!). And bearable not just for 24 weeks, but a lifetime. The Minnesota experiment tells us that when semi-starvation ends, the refeeding period will not end well.

This issue of how to diet, and how to lose weight, was in the news again recently when a study was published by researchers at the National Institutes of Health. The researchers confined their obese subjects (nine women, 10 men) to a hospital ward and then put them on diets that approached semi-starvation, feeding them an average of more than 820 fewer calories a day than they needed to maintain their weight. They averaged about 1,920 calories a day, but one diet was composed of foods that were 29 percent carbohydrates and 50 percent fat — the carb-restricted diet — and the other was composed of foods that were 71 percent carbohydrates and only 8 percent fat — the fat-restricted diet.

The subjects were then required to eat these diets, not a calorie more or less, for six days — not 24 weeks.

An N.I.H. official hailed the study as providing “invaluable evidence on how different types of calories affect metabolism and body composition.” Google News referenced well over 200 entries about the study in the first three days after publication.

What made the headlines? That the subjects lost more fat by restricting dietary fat than they did by restricting the same number of carbohydrate calories. “Scientists (sort of) settle debate on low-carb vs. low-fat diets,” as The Washington Post put it.

But the devil in nutrition studies is always in the kind of details that are encapsulated by phrases like “sort of.” Whether the evidence was invaluable, as the N.I.H. claimed, depends on a number of issues. Is the experience of six days relevant to what happens over months, years or a lifetime? There’s little reason to think so. Can humans survive (and if so, for how long) on a diet of 8 percent fat? The Food and Agriculture Organization of the United Nations has said 15 percent is the lower limit. And then is a diet with about 30 percent carbohydrates sufficiently restricted to be considered a low-carb diet — the N.I.H. diet included blueberry muffins at breakfast, spaghetti at lunch and wraps for dinner.

Those who argue publicly (as I do) that refined grains and sugars cause obesity believe that losing meaningful weight requires far more significant changes in the quality of carbohydrates consumed (far less refined) and in the amount (less than 20 percent, perhaps less than 10).

Finally, what about hunger? By inflicting caloric deprivation for only six days, the researchers seem to have made the implicit decision that hunger — the biological response to caloric deprivation — is irrelevant to how we should think about a weight-loss diet. That the subjects might be hungrier on one diet than the other was also not addressed.

The low-fat diet of the N.I.H. experiment had significantly less fat (8 percent vs. 17 percent) and only 350 more calories a day than the diet on which the Minnesota researchers drove their conscientious objectors to the point of character neurosis and mental breakdowns. The N.I.H. diet had more protein, too. But the history of diet studies (and human populations) suggests that caloric deprivation is unsustainable.

That humans or any other organism will lose weight if starved sufficiently has never been news. The trick, if such a thing exists, is finding a way to do it without hunger so weight loss can be sustained indefinitely. A selling point for carbohydrate-restricted diets has always been that you can eat to satiety; counting calories is unnecessary, so long as carbohydrates are mostly avoided.

But this advice raises a pair of obvious questions, or at least it should: If people on low-carb diets eat less (the conventional explanation for any loss of fat that ensues), why aren’t they hungry? Where’s the semi-starvation neurosis? And if they don’t eat less, why do they lose weight? It implies a mechanism of weight loss other than caloric deprivation and suggests that the carbohydrates and fats consumed make a difference.

Questions like these about the relationship between calories, macronutrients and hunger have haunted nutrition and obesity research since the late 1940s. But rarely are they asked. We believe so implicitly in the rationale of eat less, move more, that we (at least those of us who are lean) will implicitly fault the obese for their failures to sustain a calorie-restricted regimen, without ever apparently asking ourselves whether we could sustain it either. I have a colleague who spent his research career studying hunger. Asking people to eat less, he says, is like asking them to breathe less. It sounds reasonable, so long as you don’t expect them to keep it up for long.

Much of the obesity research for the past century has focused on elucidating behavioral techniques that could induce the obese to eat less, tolerate hunger better, and so, by this logic, lose weight. The obesity epidemic suggests that it has failed.

For those who believe that hunger is somehow all in the mind, rather than a powerful biological response to caloric deprivation, it is tempting to wish on them the fate that the goddess Ceres bestowed on King Erysichthon of Thessaly in Greek mythology. She “devised a punishment to rouse men’s pity… to torment him with baleful Hunger.” Erysichthon then eats himself out of castle and kingdom and ultimately dies by feeding, “little by little, on his own body.”



chris c said...


Utter bollocks! They're getting desperate. For people who've never NOT eaten a high carb diet, ketoadaptation may take a couple of weeks or more. Many anti-low-carb researchers are well aware of this and terminate the studies during this time. But SIX DAYS??? And they think this proves something.

Bob said...

Carbsane is having some fun with this one. Worth the read.

chris c said...

Sorry I'm not that much of a masochist