snacks, like meat‐flavored potato crisps or cheese‐flavored crackers, act as “protein decoys,” which are attractive when protein deficient, but rather than rebalance the deficiency, they exacerbate it through their high fat and carbohydrate content [109]. The resulting protein dilution can further drive energy over‐consumption through protein leverage. An illustration of this is the finding discussed above that subjects restricted to low‐protein diets in the experiments of Gosby et al. [57] over‐ate energy principally via snacking on savory foods between meals.
In addition to the formulations themselves, many other factors encourage the consumption of ultra‐processed foods. These include their convenience and relatively low price, the latter partly due to the low content of protein which is more expensive than fats and carbohydrates [110]. Aggressive marketing is an important factor at all scales from local food advertising and promotion to sophisticated global strategies facilitated by the transnationalization of advertising agencies and exploitation of new media technologies [111]. Marketing strategies include the “health halo” effect, in which misleading claims or imagery manipulate consumers into associating products with healthfulness. Marketing budgets of multinational processed food and beverage companies are immense. In 2018, the Swiss food and beverage producer Nestlé is reported to have spent US$7.3 billion on global advertising, and US$1.9 billion more than that in 2016 [112].
There is growing evidence that corporate political activity, whereby industries influence government policy, research, and dietary guidelines for their own benefit, significantly impedes the formulation and implementation of public health policies for reducing the intake of problem foods [103,113–115]. A recent analysis documented the strategies used by one company, Nestlé, to market processed breastmilk substitutes [116]. Strategies included: “‘information strategy’, used to fund, produce and disseminate industry‐preferred information” “[establishing] relationships with key opinion leaders and health organizations, and the media” “[seeking] involvement in the community” “directly [influencing] policies and programs through indirect access and the placement of actors in government policy settings” and using “argument‐based ‘discursive strategies’ to frame the debate on a diet‐ and public health‐related issues.”
Having reported in 2018 an annual turnover of over 92.6 billion CHF (US$101 billion) and an underlying trading operating profit of 16.3 billion CHF (US$17.9 billion), Nestlé is well resourced to execute such strategies. This is not, however, an isolated case. Similar tactics are widespread in the food industry, as in other industries where there are potential trade‐offs between public interest and corporate profit [114,117]. Collectively, their capacity to influence the global food systems and food environments is immense.
Bringing it all together: complex systems
Linking public health to the science of ecology is important, because it provides a bridge for the transfer of concepts and methods that could potentially enrich both fields. Nutritional geometry is one example, demonstrating how approaches from animal studies, both in the laboratory and in the wild, could provide fresh insight into major public health challenges, such as the obesity epidemic. Another example is the link between the “ecosystem” concept from ecology and the “food systems” concept in public health, mentioned above. We believe that the combination of these approaches holds considerable promise for reconceptualizing and potentially reversing the obesity epidemic.
As noted previously, one defining feature of the concept of the ecosystem is that it provided a framework for elevating ecological thinking beyond organisms to the broader system that includes both biological and non‐biological aspects of the environment [78]. This integrative approach inevitably directed the attention of ecologists towards questions of how the interactions among the component parts of the system influence the properties and behavior of the system, a quest that has yielded many powerful ecological insights that are relevant also to public health.
One key insight is that the properties of interacting components of ecosystems (e.g. individuals, populations, species) can be changed as a result of their interactions with other components through a process known as “adaptation”. Those changes can reverberate through the system, eliciting adaptations in other interacting components, which can drive further changes in the first, producing a dynamic reciprocal process known as “coevolution” [118]. Important properties of ecosystems, such as the degree of stability and productivity, “emerge” from these adaptive and coevolutionary dynamics among its components. The ecosystem‐level properties can, in turn, feed back to influence the properties of the interacting components [119]. Systems that are interconnected in this way via feedback loops within and across scales, known as “complex adaptive systems,” are fundamentally different from traditionally engineered systems and often show counter‐intuitive behavior that defies simple cause‐effect expectations. They take on a life of their own that cannot be understood or managed as would an engineering problem.
The realization that food systems, like ecosystems, are complex adaptive systems [120] could hold the key to reconceptualizing public health nutrition in ways that deliver fundamental change. It could help to explain, for example, why nutrition transitions that are unquestionably linked to immense national, social, and individual cost are so inevitable in their genesis, inexorable in their progression and trenchant in their persistence, despite well‐meaning and often costly policy interventions. One reason is that measures aimed at mitigating the impacts of nutrition transitions can drive adaptation and coevolution that cause unanticipated effects that nullify the measure, exacerbate the problem, or create new problems.
An example is mentioned above, where the recommendation in the US dietary guidelines to reduce fat intake caused a shift in consumer choice towards high carbohydrate foods. Not only did the food industry respond to meet the demand, but it further intensified it through marketing strategies predicated on the supposed benefits of low‐fat (high carbohydrate) products. The consequence was a rapidly changed food system that did not solve the obesity crisis but rather created further problems.
One of those problems is the loss of trust in national dietary guidelines [102,115] and, as mentioned above, the emergence of extreme diet philosophies that vilify dietary carbohydrates in whatever form, despite the fact that many of the healthiest dietary patterns, such as the traditional Okinawan diet, are high in carbohydrate [121,122]. Failure to distinguish between healthy and unhealthy forms of carbohydrate has led to blanket demonization of all carbohydrates [123]. This, in turn, paved the way for an even more prolific and lucrative commercial sector marketing alternative diet philosophies, many leveraging off the tarnished reputation of carbohydrates. Since carbohydrate is, with few exceptions (e.g. the traditional Inuit diet), the major source of dietary calories, removing them or reducing them significantly inevitably results in increased fat intake. Whatever the direct health consequences of that, increasing fat to the extent required to maintain protein around healthy levels for humans would involve eating a diet of 80–90% fat, which would not be sustainable for most humans. Consequently, low carbohydrate diets are also usually high in protein [124]. While this might be beneficial in the short term for weight loss or clinical management of obesity and diabetes [122,125], principally because of protein leverage, there is evidence that high protein diets, especially when combined with low carbohydrate, accelerate aging and the onset of associated diseases [126]. Furthermore, as discussed above, high protein diets can in the long‐term cause obesity by exacerbating protein leverage through decreasing protein efficiency, and obesity can itself feed into this process by increasing the breakdown of lean tissue and hepatic gluconeogenesis [53].
Effective management of such complex systems cannot be devised using conventional engineering approaches which assume the interactions among the components are linear – i.e. not characterized by myriad feedbacks. Among the impediments that arise are two common biases that distort the nature of the challenge [127]. The first of these, the “hierarchical bias,” assumes the system has a strong top‐down organization and thus that top‐down interventions will be effective. As discussed in relation to dietary guidelines, this fails to appreciate that the system might
