The UN Food and Agriculture Organization has been assessing human energy requirements for years, but increasing levels of overweight and obesity over the last 25 years have forced it to make changes to the way it calculates these needs. Indeed, further changes have been proposed to take into account different levels of activity, as Kate Barker reports.

At a recent conference organised by the International Obesity TaskForce at the London School of Hygiene and Tropical Medicine, experts in health and nutrition gathered to discuss the global obesity epidemic and, in particular, whether energy needs have been overestimated in the last 20 years, thereby exacerbating the obesity problem.

Assessing the energy and nutrient needs of humans has been one of the central mandates of the Food and Agriculture Organization of the United Nations (FAO) since its inception. Assessing energy and nutrient requirements is vital for deciding whether food supplies are sufficient to meet nutritional needs and also for assessing the proportion of people, whether nationally, regionally or globally, who do not have access to sufficient nutrients and are therefore considered to be undernourished. However, for the first time, the number of overweight individuals worldwide rivals those who are underweight. According to the FAO, chronic hunger affects around 852 million people worldwide, while the number of overweight or obese people worldwide is estimated to be more than one billion.

“We believe obesity is a significant problem that needs to be dealt with, along with the problem of the underfed,” says Prakash Shetty, chief of the FAO’s Nutrition Planning, Assessment and Evaluation service.

A few years ago such a statement would have been rare, but now the FAO can use its assessment of energy needs to estimate numbers of people with access to excess food, not just the food-deprived.

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Obesity becomes widespread

And it’s not just a problem for the developed world; a 1999 United Nations study found obesity was on the increase in all developing regions, even in countries where hunger exists.

In China, the number of overweight people jumped from less than 10% to 15% in just three years. In Brazil and Colombia, the figure is around 40% – a level comparable to a number of European countries. Even in sub-Saharan Africa, where most of the world’s hungry live, obesity levels are on the increase, especially among urban women. While the world produces enough food to feed its entire population, the food does not always get to those who need it, resulting in hunger among some people and obesity among others.

The obesity problem has led to the FAO and World Health Organization (WHO) re-evaluating energy requirements for all age groups to base them on measurements and estimates of daily energy expenditure. In the case of infants and children, energy expenditure also includes energy needed for growth. This has led to the modification of estimated energy requirements for infants, children and adolescents. The new mean recommendation values for infants are 5-10% lower than previous estimates for the first year of life. Current recommendations based on expenditure are also substantially lower for children up to ten years of age, compared to previous recommendations used in 1985 by the FAO and WHO based on observed food intake.

In its 2001 report on human energy requirements, the first to calculate energy needs based on daily energy expenditure, the FAO also proposed differentiating the requirements for populations with lifestyles that involve different levels of habitual physical activity.

Are all calories equal?

But the obesity problem is not simply a case of energy requirements versus energy output. Many overweight people also suffer from a lack of vitamins and minerals, referred to as micronutrient deficiency.

“The thinking used to be that if people get enough energy in their diets, the micronutrients will take care of themselves,” says Barbara Burlingame, senior officer in FAO’s Nutrition Impact Assessment and Evaluation Group. “But increasingly people are eating larger quantities of cheap food that fill the stomach but still leave the body without those micronutrients.”

And this raises the issue of food quality in relation to energy balance, and the question: are all calories equal? This question was posed by one of the conference’s speakers, Professor Andrew Prentice of the MRC International Nutrition Group and the London School of Hygiene and Tropical Medicine.

He interprets food quality as the macronutrient balance within individual foods, where the four major energy-giving macronutrients are fat, carbohydrate, protein and alcohol. Current evidence suggests the macronutrient composition of diets affects ingestive behaviour such as appetite and satiety.

“In general, high-fat diets have high energy density and readily promote over-consumption,” Prentice says. “In malnourished children a high energy density is desirable to promote catch-up growth, but in others it has the undesirable effect of promoting obesity.”

Energy density and over-consumption

Research suggests that people eat the same bulk of food even if the fat content is higher. In one experiment, participants had access to food that had different proportions of fat content and were asked to eat normally. Food was altered so that some participants had food that contained 20% fat, while others had 40% or 60% fat content. The subjects, who were unaware of the fat content of their particular diet, ate the same bulk of food regardless and so those with the higher fat diets were passively over-consuming and had a much higher calorie intake. The results suggest that the higher the energy density of the food, the more calories will be consumed.

This is particularly relevant to childhood obesity. Children are often attracted to fastfood and junk food, which tends to be energy dense. And while children may have good natural appetite control, energy dense foods disrupt this and encourage over-consumption.

Prentice also brought up the issue of low-carbohydrate diets, and the hypothesis that diets low in protein may stimulate over-consumption of energy because excess non-protein energy would have to be consumed in order to obtain a sufficient amount of protein. In other words, the body requires a certain amount of protein and people are likely to keep eating until this amount is reached, regardless of how many calories are consumed. Thus, low-protein diets are likely to stimulate over-consumption of carbohydrates and therefore a higher energy intake, whereas with high-protein diets energy intake is regulated.
Trend toward unhealthy diets

Diets today, and in the foreseeable future, do not comply with dietary recommendations made by a consultation of health experts convened by the FAO and WHO last year. According to the study, 36% of all countries in the world already have populations consuming above the recommended maximum level of 300 milligrams per person per day of cholesterol, more than twice the rate of the early 1960s.

Likewise, 34% of all countries exceed the 30% threshold of fat in the diet, compared to 18% 40 years ago. The FAO estimates that more than 40% of the additional calories consumed in the future will come from fats.

So, what can be done? The mood at the conference was, at times, downbeat, as experts warned that the situation was unlikely to improve without major policy changes. Evidence should determine good health policies, but nutritionists expressed their anger and depression that evidence of the obesity problem has been around for years yet there has been little political interest, and it has been “business as usual” from the world of commerce. And while some countries in the developed world are beginning to address the issue, the situation in developing countries is likely to deteriorate, especially with the increasing availability of fastfood.

Finland sets an example

But there was a glimmer of light at the end of the tunnel. Finland was mentioned several times as a success story when it comes to fighting obesity. Being labelled the unhealthiest nation in the world in terms of the prevalence of heart disease in 1970 spurred the Scandinavian country into action, and it has managed to decrease the number of men dying from cardiovascular heart disease by 65%. Life expectancy has risen by seven years for men and six years for women.

Pekka Puska, director of the National Institute of Public Health in Helsinki told The Guardian recently that the key to this success was positive reinforcement. Instead of bombarding people with messages telling them what not to do, the country gave whole communities incentives to improve their health. Towns were pitted against each other to see which could lower their cholesterol the most. “We didn’t tell people how to cut cholesterol, they knew that. It wasn’t education they needed, it was motivation. They needed to do it for themselves,” Puska told the newspaper.

But it wasn’t simply down to motivation; huge policy changes were also implemented. Tobacco advertising was banned outright. Farmers were encouraged to produce low-fat milk, and payment was linked to how much protein meat and dairy contained, rather that how much fat it contained. Some people had argued that calls to eat more fruit would mean more imported produce, so instead officials encouraged the growing of berries, such as redcurrants and blackberries, which thrive in the country’s climate. The government also had some success in cutting salt intake, something the UK is attempting at the moment.

A bleak outlook?

But one of Finland’s biggest successes was to persuade an inactive nation to take regular exercise despite the country’s cold climate. The standard and accessibility of exercise facilities were improved, and people were encouraged to cycle, walk, go cross-country skiing or play ball games. New walking and cycle paths were built to persuade people to incorporate more exercise into their daily regime.

Although Finland still has work to do – some surveys suggest that 40% of men and 35% of women are still not active enough – it continues to be cited as an example of how a nation can change. But one thing is clear – such an initiative not only needs firm political backing, but also huge public support. Back at the conference in London there was widespread agreement that more has to be done to tackle the global obesity epidemic, and there was little doubt that the future looks bleak.