A groundbreaking study from the University of Auckland has pulled back the curtain on the food industry's secretive playbook, revealing how ultra-processed foods—commonly known as junk food—are meticulously engineered and marketed to hijack our appetites and promote overeating. Led by Dr. Joshua Clark and published in Obesity Reviews, the research maps out 11 interconnected feedback loops that make these products irresistible, contributing to New Zealand's escalating obesity crisis.

This work builds on a growing body of evidence showing that these foods transcend simple indulgence; they are designed with precision to exploit human biology, bypassing natural satiety signals and fueling chronic overconsumption. For Kiwis, where ultra-processed foods now account for around 50 to 60 percent of daily energy intake, the findings underscore an urgent public health challenge.

Defining Ultra-Processed and Hyper-Palatable Foods

Ultra-processed foods (UPFs) represent the most industrialized end of the food spectrum. According to the NOVA classification system—developed by researchers at the University of São Paulo and widely adopted globally—UPFs are formulations of ingredients, often cheap extracts from foods like oils, sugars, and starches, combined with additives such as emulsifiers, flavors, colors, and preservatives. Unlike minimally processed items like fresh vegetables or whole grains, UPFs rarely contain recognizable whole foods and are created primarily for commercial appeal and shelf stability.

Within UPFs lies a subset known as hyper-palatable foods (HPFs), first quantitatively defined by Tera Fazzino at the University of Kansas. HPFs feature specific ratios of fat and carbohydrates (around 14 percent fat and 45 percent carbs), fat and sodium (around 16 percent fat and 8 percent sodium), or simple carbs and sodium (around 25 percent carbs and 1.6 percent sodium). These combinations trigger intense reward responses in the brain, similar to addictive substances, leading to passive overeating where people consume far more calories without realizing it.

In New Zealand supermarkets, UPFs dominate about 70 percent of packaged products, from sugary cereals and soft drinks to savory snacks and ready meals. The Auckland team's causal loop diagrams illustrate how these formulations create a self-perpetuating cycle of craving and consumption.

Engineering Overeating: The Formulation Science

The design process for UPFs begins with food scientists—often called flavorists—fine-tuning ingredient blends to hit 'bliss points,' the optimal sensory peaks for pleasure. Step one involves selecting base ingredients: refined sugars for quick energy hits, fats for mouthfeel and prolonged satisfaction, and salts for flavor enhancement. These are processed to alter texture—extrusion for crispiness in chips, homogenization for creamy sauces—reducing chew time and speeding digestion, which blunts fullness signals from hormones like leptin and cholecystokinin.

Chemical additives play a starring role. Emulsifiers like lecithin ensure smooth textures, while artificial sweeteners and high-fructose corn syrup provide sweetness without bulk. Enzymes break down starches for rapid glucose spikes, mimicking natural rewards but amplified. The result? Foods that dissolve quickly in the mouth, releasing flavors intensely while minimizing effort, encouraging bite after bite.

Dr. Kelly Garton, senior author, notes that UPF producers borrowed from tobacco industry tactics in the 1980s, acquiring flavor houses to engineer hyper-palatability. A companion study in Addiction details how these chemical tweaks make UPFs exceptionally profitable—cheap to produce, long-lasting, and engineered for addiction-like consumption patterns.

The 11 Feedback Loops Driving Consumption

At the heart of the Auckland study are causal loop diagrams depicting 11 reinforcing feedback loops. These interconnected mechanisms trap consumers: one loop shows how repeated exposure conditions taste preferences toward UPFs, shifting norms away from whole foods. Another exploits convenience—UPFs require no prep, fitting busy lifestyles while displacing cooking traditions.

• Biological hijack: Fat-carb-sodium combos activate dopamine pathways, overriding hunger cues.
• Behavioral conditioning: Quick rewards build habits, making UPFs the default choice.
• Social normalization: Marketing embeds UPFs in celebrations, family routines, and kids' events.
• Economic pull: Low costs and high margins incentivize aggressive promotion.

These loops amplify each other; for instance, hyper-palatability boosts sales data, refining targeting algorithms for personalized ads. The study's workshop-validated models provide a blueprint for policymakers to target interventions.

Marketing Mastery: From Kids to Algorithms

UPF companies invest billions in marketing that complements engineering. In New Zealand, child-targeted tactics dominate: cartoons on packaging, tie-ins with popular media, and placements near schools. Digital surveillance tracks online behaviors for hyper-personalized ads on social platforms, creating echo chambers of temptation.

Strategic retail: eye-level shelf placement, end-of-aisle displays, and buy-one-get-one deals exploit impulse buys. Branding illusions of health—'low-fat' labels on still-HPF products—mislead shoppers. Prof. Boyd Swinburn highlights: "The food environment is rigged against us, with UPFs positioned as fun, affordable, and inevitable."

A 2022 evidence snapshot from Auckland researchers documents pervasive unhealthy food marketing to NZ youth and parents, underscoring the need for restrictions.

UPF Dominance in New Zealand Diets

Estimates peg UPFs at 50-60 percent of Kiwi energy intake, mirroring Australia. Imports surged from 9 percent in 1990 to 22 percent in 2023, per Garton et al. in Globalization and Health. Household purchases lean heavily UPF, with preschoolers deriving nearly half their calories from them.

This shift correlates with stagnant national nutrition surveys—last adult data from 2008/09. Rising UPF availability tracks obesity climbs: one in three adults and one in ten children obese, NZ second in OECD for child rates.

Health Toll: Beyond Weight Gain

High UPF diets fuel New Zealand's chronic disease epidemic. Unhealthy eating causes 18 percent of preventable deaths/disability. Links to type 2 diabetes (prevalence doubled last 20 years), heart disease, cancers, and depression are robust, per recent Lancet series. Mechanisms include inflammation from additives, gut microbiome disruption, and rapid blood sugar spikes.

Children face lifelong risks: early UPF exposure programs preferences, raising obesity odds. NZ's child obesity rate, second-highest OECD, demands action.

Voices from the Researchers

Dr. Joshua Clark: "UPF manufacturers exploit biology and behavior in clever, interconnected ways that hook populations." Garton: "It's a system prioritizing profit over health." Swinburn: "NZ lags; we need SSB taxes, ad bans, labels like Latin America." Their interdisciplinary approach—food science, marketing, systems modeling—sets a model for university-led impact.

Global Lessons and Policy Pathways

Latin America leads: Mexico's junk food tax cut SSB sales 10 percent; Chile's child ad bans and labels reduced purchases. Over 50 countries tax SSBs. NZ could adopt front-of-pack warnings, lobby transparency, school UPF restrictions.

WHO urges UPF curbs; Auckland researchers advocate aligning guidelines explicitly against UPFs.

U Auckland's Role in Fighting the Obesity Epidemic

The University of Auckland's School of Population Health spearheads NZ nutrition research, from UPF mapping to policy briefs. Collaborations yield tools like causal diagrams for advocacy. This positions U Auckland as a hub for public health careers, training experts in epidemiology, food systems, and behavioral science.

Photo by Yulin Wang on Unsplash

Future Outlook: Reclaiming Food Environments

Optimism lies in evidence: policies work. NZ can pivot via updated dietary guidelines, taxes funding healthy food access. Universities drive innovation—AI for reformulation, community trials. Individuals: prioritize whole foods, support labels. The Auckland study empowers change, turning awareness into action against engineered overeating.

For those passionate about nutrition, opportunities abound in NZ higher ed: lecturer roles at U Auckland, research posts tackling diet-related diseases. Explore paths in public health, advancing solutions from lab to policy.