TOWARDS 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: wholewheat bread, potatoes, cereals and considerable amounts of turnips and cabbage with token amounts of meat and dairy products. As diets go, it was what nutritionists today would consider a low-calorie, and very low-fat diet, with only 17% of calories coming from fat.
What happened to these men is a lesson in our ability to deal with caloric deprivation, which means a lesson in any expectations we might have about most current weight-loss advice as well.
The men lost an average of half-a-kilogram of body fat a week over the first 12 weeks, but averaged only 250g 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 cold; and 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.
The Minnesota researchers called this “semi-starvation neurosis”. Four of their subjects developed “character neurosis”. Two had breakdowns, one with “weeping, talk of suicide and threats of violence”. The “personality deterioration” of the other “culminated in two attempts at self-mutilation”. He nearly detached the tip of one finger and chopped off three with an axe.
When the period of 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.
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% more body fat than when the experiment began — “post-starvation obesity”, the researchers called it.
Implicit in many discussions of how best to lose weight is the assumption that hunger is not an issue. Health and government organisations tell the obese and overweight to do what the study’s subjects did: eat less. That advice implies that the ensuing hunger will be an easily bearable burden — 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 US 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 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% carbohydrates and 50% fat. The other comprised foods that were 71% carbohydrates and only 8% fat.
The subjects were then required to eat these diets, not a calorie more or less, for six days.
A National Institutes of Health official hailed the study as providing “invaluable evidence on how different types of calories affect metabolism and body composition”. Google News referenced more than 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 whether the evidence was invaluable, as the National Institutes of Health claimed, depends on a number of issues. Is the experience of six days relevant to what happens over months, years or a lifetime?
Can humans survive (and if so, for how long) on a diet of 8% fat? The Food and Agriculture Organisation of the United Nations has said 15% is the lower limit. And is a diet with about 30% carbohydrates sufficiently restricted to be considered a low-carb diet?
Those who argue 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%, perhaps less than 10%).
By inflicting caloric deprivation for only six days, the researchers seem to have decided that hunger — the biological response to caloric deprivation — is irrelevant to how we should think about a weight-loss diet.
The low-fat diet of the National Institutes of Health experiment had significantly less fat (8% vs 17%) 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.
It had more protein, too. But the history of diet studies (and human populations) suggests 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: if people on low-carb diets eat less, 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 about the relationship between calories, macronutrients and hunger have haunted nutrition and obesity research since the late 1940s. But rarely are they asked.
Much of the obesity research for the past century has focused on elucidating behavioural 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.
New York Times