Most of us are either endomorphs or ectomorphs. Good examples of how these two types of body build react to low energy intakes are provided by the Survivor TV series.
The Survivor participants are actually like experimental subjects undergoing a diet trial. Since they're isolated for a number of weeks, during which time they follow a restricted and monotonous diet and do relatively hard physical labour, they give us insight into the mysteries of weight loss.
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The ectomorphs
Most of the Survivors in most of the series are ectomorphs. In other words, they're lean to begin with, have more muscle than fat tissue, have a higher metabolic rate and tend to be more physically active.
They start their adventure with only small reserves of fat. As the show progresses, they keep getting thinner and thinner.
This is one of the ironies of weight control. People who are thin tend to get even thinner if they follow a minimalistic diet.
All the factors listed above play a role: their lack of body-fat reserves, the higher muscle tissue content in their bodies, their higher basic metabolic rates due to a greater amount of lean muscle tissue and their tendency to be more active.
Added to this is an aversion to eating unfamiliar foods and the role of emotional factors.
The endomorphs
In Survivor Palau, we had an exception to the rule when it comes to body build. Most of the women are obviously selected as 'eye candy' with svelte figures, which automatically requires them to be ectomorphs.
But sometimes there is a participant, such as Katie from the Survivor Palau series, who is an endomorph. Like other endomorphs, she was plump, particularly in the abdominal and thigh areas (typical of her female gender), had a higher percentage of body fat, was less inclined to be physically active, tended to conserve her energy and ate more.
It was fascinating to watch Katie not only resist weight loss, but actually appear to gain more weight as the series progressed. She was actively conserving her stores of body fat both by eating more and doing less.
This also indicates that she is probably one of those people who have 'thrifty genes'. Scientists have discovered that many people who struggle to lose weight have such economic genes.
These genes, and the tendency to conserve the fat reserves of the body, are the result of millions of years of human survival under conditions of feast and famine. In most populations through the millennia, food was only plentiful for brief periods and most of the time populations were on the brink of starvation.
The human body is marvellously adaptive, so our forefathers learned to store fat during the good times and resist losing this precious energy store in the lean times.
Katie is a good example of a 'thrift gene carrier'. She not only conserved her fat stores by being as inactive as possible, but managed to gain weight by eating more of the highly unappetising food the Survivors were stuck with.
Another contributing factor was probably the fact that the staple food in this series was coconut meat, which can contain as much as 35% of fat (mainly saturated fat) per 100g.
Island living a factor
In series where the Survivors used a starch staple like rice, they all lost weight. This only shows that because carbohydrates contain less energy (16 kJ/g) than fat (37 kJ/g), eating carbs can actually make you lose weight.
It was also striking that the Palau Islanders, who came to show these Survivors how to fish, were all plump with similar builds to Katie. They had an excess of abdominal fat and all looked very well fed.
Living on an island, one can imagine that the local inhabitants would have been regularly exposed to periods of feast or famine throughout their history. They would also have learned to conserve their fat reserves against future periods of starvation.
Ironically, such populations throughout the world have all succumbed to pronounced metabolic derangements when confronted with the plenty of the western diet.
Populations such as the Pima Indians in America, many island populations and even our own South African indigenous people who once were thin and active, have become overweight and have to contend with all the diseases of western civilisation (such as diabetes and high blood pressure) now that they've started eating high-energy, western foods.
Katie is someone who will always struggle to lose weight – her endomorphic body build and the 'thrifty genes' she has been blessed with, will make weight loss difficult.
Thus the Survivor Palau series clearly illustrated the dilemmas that overweight people face. If you are thin to begin with, you will find it easy to lose even more weight, but if you start out with excess body fat, you will struggle to get rid of it.
- (Dr Ingrid van Heerden, DietDoc, updated August 2008)
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