The Triple Burden of Malnutrition in the Era of Globalization

Introduction

The term “triple burden of malnutrition” refers to the coexistence of undernutrition (stunting and wasting), micronutrient deficiencies (often termed hidden hunger), and overnutrition (overweight and obesity) (Fig. 1). 

Globally, there is a strong inverse association between a country’s wealth measured as gross domestic product (GDP), undernutrition, and levels of micronutrient deficiencies (Fig. 2 ^{[1, 2]}). As countries pass through the economic transition and gain in wealth, it is gratifying to see that rates of undernutrition decline rapidly. But conversely, rates of overnutrition seem to inexorably grow with increasing wealth (Fig. 3). This overcorrection has not yet been successfully avoided by any emerging nation.

The three elements of the triple burden of malnutrition can be found simultaneously within many low-income populations and even within single families ^[3–5]. Initially, overweight and obesity are confined to the wealthier sectors of emerging societies, but after a decade or two, the demographic association flips and overweight becomes more prevalent among the poorer strata ^{[6, 7]}. 

There are common underlying causes to each element of the triple burden of malnutrition ^[8]. In broad terms these are as follows: poverty – a lack of access to the most nourishing foods; poor dietary choices – a lack of knowledge about what constitutes the most nourishing foods and a healthy diet; and food supply chain – production and marketing of cheap, low-quality foods. Some of these may be exacerbated by future threats to the food supply chain arising from climate change and a degraded planet.

It can be argued that the underlying influence of these distal factors are channeled through a single proximal cause – namely a low nutrient density of foods as summarized below.

Undernutrition

Stunting and wasting result from deficits of energy and protein supply. These deficits are often, but not always, consequent upon a poor dietary supply. Examination of aggregated growth curves from low- and middle-income countries reveals a precipitate decrease in weight, and especially in height z-scores in the first 2 years of life with a stabilization thereafter ^[9]. There is strong evidence to suggest that, in addition to the influence of low-quality weaning foods, infections are an important contributory cause and that nutrient deficits are exacerbated by a combination of loss of appetite, episodic periods of acute weight loss, chronic suppression of the insulin-like growth factor axis consequent upon inflammation, and nutrient malabsorption caused by chronic gut damage (so-called environmental enteric disease) ^[10].

In the light of this understanding of the important role of infections in driving undernutrition, there was great hope that implementation of water, sanitation and hygiene (WASH) interventions would reduce the prevalence of diarrhea and environmental enteric disease and hence improve growth. Three large randomized trials in Bangladesh, Kenya, and Zimbabwe tested the impact of improved WASH (with and without advice on infant and young child feeding based upon WHO’s recommended best practice) ^[11–13]. Disappointingly, the WASH interventions did not improve linear growth. It seems likely that the absence of impact can be attributed to the fact that there is a high hygiene threshold that must be overcome ^[14], and this has led to calls for so-called “transformative WASH” ^[15].

The importance of having a high energy density in the weaning diets of undernourished infants was elegantly demonstrated in a small intervention trial from Bangladesh [16]. This trial illustrates how manipulation of the energy density of weaning foods, together with enhanced feeding frequency, can greatly increase overall energy intakes in partially breastfed infants ^[16]. The investigators studied 18 stunted Bangladeshi infants aged 8–11 months. They offered 3 different complementary weaning foods with energy densities of 0.5, 1.0, or 1.5 kcal/g on 3, 4, or 5 occasions a day. The mothers were encouraged to continue breastfeeding as usual and breast milk intake was assessed by test weighing. Increasing the energy density and increasing the feed frequency of the weaning food each independently increased the weanlings’ overall energy intake. There was a small consequent reduction in breast milk intake, but, even accounting for this, there were clear increases in energy intake as summarized in Figure 4.

This example can be extrapolated to other nutrients for which a higher nutrient density would inevitably provide a higher overall nutrient intake. In fact, given that other nutrients would not suppress breast milk intake as was the case for energy, the net benefits would be even greater. It should be noted also that a high nutrient content of diets is especially important in periods when children are attempting catch-up growth as is frequently the case after infection-related bouts of weight faltering ^{[17, 18]}.

Micronutrient Deficiencies

It is self-evident that most micronutrient deficiencies are caused by a low nutrient density of diets (which generally arises from low dietary diversity and poor access to animal-sourced foods) and that consumption of higher-quality diets is constrained by multiple factors in poor populations (as summarized by Black et al. ^[3]). Consequently, there tend to be strong associations between deficiencies of different micronutrients; a child deficient in one micronutrient will, in general, suffer from multiple deficiencies.