Why “just eat better” is advice that ignores the arithmetic of poverty, and what would actually change the math.
In January 2024, Nigeria’s National Bureau of Statistics began publishing something it had never tracked before: the Cost of a Healthy Diet. The number it produced was uncomfortable.
By the time the UN’s flagship food security report was released that year, the finding was stark – upwards of 79% of Nigerians could not afford a healthy diet.
Not “chose not to eat one.” Could not afford one.
What happened next is the interesting part. The figure became a negotiating tool. When Nigeria’s government sat down to revise the national minimum wage in mid-2024, the cost of a healthy diet featured heavily in the talks, and the wage was eventually more than doubled. A nutrition statistic had quietly become an economic one.
That move tells you something important about malnutrition in places like Nigeria.
We tend to treat poor diets as a problem of behaviour – of people not knowing what to eat, or not caring enough to choose well. Public health campaigns are built on that assumption.
But the deeper problem is not that people don’t know vegetables are good for them. It is that, for a large share of the population, the healthy choice is the expensive choice, and the body responds rationally to prices. If we want people to eat better, we have to make better cheaper.
Telling them to try harder will not do it.
The arithmetic of a cheap calorie
Start with a fact that holds almost everywhere researchers have looked. Energy-dense foods built from refined grains, added sugars, and cheap fats are cheaper per calorie than nutrient-dense foods like vegetables, fruit, pulses, fish, and animal protein.
A systematic review of studies across multiple countries found the pattern was unanimous: the foods that fill you up for the least money are reliably the ones that nourish you least.
The World Bank’s own data put hard numbers on the gap.
Using internationally comparable prices, the cost per day of just enough dietary energy from the cheapest local starchy staple is about $0.83. The cost of a diet that actually meets nutrient needs is roughly $2.44. A genuinely healthy diet runs higher still – the 2025 SOFI report put the global average at $4.46 per person per day. In other words, escaping hunger is cheap. Escaping malnutrition costs roughly three to five times as much.
Now apply a household budget to that gap. If you are living close to the poverty line, your food spending is not optimising for iron or vitamin A. It is optimising for the cheapest way to stop being hungry, today, for everyone at the table. Refined cassava, white rice, palm oil, sugar, and bread win that contest every time.
The Lancet Planetary Health estimated that a nutrient-adequate diet exceeds available income for everyone living in extreme poverty. The healthy plate is not slightly out of reach. It is structurally out of reach.
This is why “hidden hunger” – micronutrient deficiency – so often hides behind a full stomach. A child can eat enough calories and still be short of the iron, zinc, vitamin A, and protein that build a body and a brain. The hunger you can see has a cheap fix. The hunger you cannot see does not.
The strange shape of malnutrition
When cheap calories are the rational choice, the result is not simply undernutrition. It is something stranger, and Nigeria shows it clearly.
The country still carries one of the heaviest burdens of child undernutrition in the world. Around 32% of Nigerian children under five are stunted – too short for their age, a marker of chronic nutritional deficit during the years when it does permanent damage. Only about 17% of babies are exclusively breastfed for their first six months. Malnutrition is a direct or underlying cause of nearly half of all under-five deaths.
And yet, at the same time, overweight and obesity are rising, especially among adults in cities. One analysis of national survey data found that while child stunting barely moved between 2003 and 2018, maternal obesity rose by 71% over the same period. Researchers increasingly find both conditions inside the same household – an overweight mother and an undernourished child sharing one kitchen. This is the “double burden of malnutrition,” and it is well documented in Nigeria.
It looks like a contradiction. It is not. It is exactly what you would expect when the cheapest available calories are energy-dense and nutrient-poor. The same food economy that leaves a child stunted can leave an adult overweight, because both outcomes flow from a diet heavy in refined starch and oil and light in everything else.
Nigeria is in the middle of what nutritionists call the nutrition transition: as incomes shift and cities grow, traditional diets give way to processed, energy-dense food faster than they give way to better food. Consumption of sugar-sweetened beverages in Nigeria rose by 39% in recent years, while consumption of vegetables and pulses fell by 7%. Five of the country’s top ten risk factors for death and disability are now diet-related.
Why “eat better” keeps failing
If the problem were really ignorance, nutrition education would fix it.
Often, it doesn’t – or it produces far less than its cost would suggest. The reason is simple once you accept the economics: you cannot health-message your way past a budget constraint. A mother who is told her child needs more eggs, more leafy vegetables, and more fish is not learning anything she doesn’t already suspect. She is being told to buy the items at the top of the price-per-calorie ladder on an income that is already stretched to the bottom rung.
This is the same logic that explains why a cheap, proven intervention can sit unused for years. It is not that people reject the better option. It is that the better option asks something of them – money, time, access – that the situation can’t supply. When advice and arithmetic disagree, arithmetic wins.
There is also a quieter unfairness buried in the numbers.
The cost of nutrient adequacy is highest for adolescents and for women who are pregnant or breastfeeding – precisely the groups whose nutrition matters most for the next generation. The people for whom a good diet would do the most good are the people for whom it costs the most.
What actually changes the math
If the problem is price, then the solutions worth taking seriously are the ones that change price or availability, not the ones that simply repeat the advice more loudly.
The most efficient is fortification: adding micronutrients to the cheap foods people already buy, rather than asking them to buy different foods.
Nigeria already mandates the fortification of staples like flour, sugar, and vegetable oil. It works precisely because it doesn’t depend on changing behaviour or budgets – it meets people at the food they can already afford. The catch is enforcement; mandates on paper mean little if compliance isn’t monitored. But the underlying logic is the right one: make the cheap calorie a better calorie.
School feeding does something similar by a different route. A free, nutritious midday meal reaches the child directly, bypassing the household budget entirely, and tends to improve attendance and learning at the same time. It is one of the higher-return public investments available, which is why its funding gaps are so frustrating.
Targeted support and wages matter too – and Nigeria’s own minimum wage episode is the proof. When the cost of a healthy diet was treated as an income problem rather than an information problem, the policy response was to raise incomes. Whether that wage rise survives inflation is a separate question, but the framing was correct: affordability is the lever.
And then there is agricultural and trade policy, the least visible but most powerful of all. What is cheap on a market stall is not an accident; it is the downstream result of decisions about what gets grown, subsidised, imported, and taxed.
A food system that makes refined starch the cheapest thing on the shelf is a policy choice, even when no one chose it on purpose. Changing what is cheap is harder than running another awareness campaign, but it is the only thing that addresses the actual constraint.
The reframe
None of this means nutrition knowledge is worthless, or that personal choices don’t matter. They do. But for a large share of people in countries like Nigeria, the binding constraint is not what they know. It is what they can afford. As long as the healthiest plate is also the most expensive one, the rational, loving, budget-conscious decision will keep being the one that quietly harms the people making it.
The real intervention, then, is not teaching the poor to choose better. It is changing a food system that has made the healthy choice the expensive one. Nigeria took one small step in that direction when it let a nutrition statistic reshape a wage negotiation.
The deeper work is to keep treating malnutrition as what it largely is – not a failure of knowledge, but a problem of price.
