People on tight budgets are often told that eating well is simply a matter of better choices. The research on food prices and on how financial pressure affects thinking suggests the picture is more complicated. Healthier diets tend to cost more, the gap has at times grown, and the worry that comes with not having enough money appears to make every kind of decision harder, including what to buy and what to cook.
None of these findings means that low-income households cannot eat well, and many do. But together they help explain why diets so often change when money gets short, and why that change is not simply a failure of willpower.
The price of a healthier plate
The most widely cited estimate of the cost difference comes from a 2013 meta-analysis led by Mayuree Rao and Dariush Mozaffarian at the Harvard School of Public Health, published in BMJ Open. The team pooled 27 studies from 10 high-income countries that compared the prices of foods and diet patterns.
According to the Harvard Gazette‘s report on the study, the healthiest diets, rich in fruits, vegetables, fish and nuts, cost about US$1.50 more per day than the least healthy diets, which leaned on processed foods, meats and refined grains. That figure was calculated per 2,000 calories, a typical adult’s daily intake, and works out to roughly US$550 per person per year.
Mozaffarian noted that “the difference was smaller than many people might have expected.” For a household already struggling, however, an extra US$550 a year per person, multiplied across a family, is not trivial.
Why cheap calories are so cheap
Part of the explanation lies in how foods are priced. Researchers at the University of Washington have studied what they call energy density, the number of calories in each gram of food. Calorie-dense foods, often those high in refined grains, added sugars and fats, tend to cost less per calorie.
In a study published in 2007 in the Journal of the American Dietetic Association, Pablo Monsivais and Adam Drewnowski tracked supermarket prices in the Seattle area in 2004 and again in 2006. According to the university’s release, the prices of lower-calorie foods rose about 19.5% over those two years, while the most calorie-rich foods stayed stable or even fell slightly. General food price inflation over the same period was about 5%.
“That the cost of healthful foods is outpacing inflation is a major problem,” Drewnowski said at the time. The study covered one city over a short period, and prices have moved in many directions since. But it illustrates a pressure that makes cheaper, more filling foods the rational choice for a shopper trying to stretch a fixed amount of money across a week.
What financial worry does to thinking
Cost is only part of the story. A separate line of research suggests that being short of money also affects the mental resources people bring to every decision, including those about food.
In a 2013 paper in Science, Mani, Mullainathan, Shafir and Zhao reported two sets of experiments. In the first, about 400 shoppers at a New Jersey mall were asked to think through how they would pay for an unexpected car repair. For some, the repair cost about US$150. For others, it cost about US$1,500. While they considered the problem, they completed standard tests of reasoning and mental control.
According to Princeton University’s release on the study, poorer and wealthier participants performed about the same when the repair was cheap. When it was expensive, the lower-income participants performed significantly worse, while the wealthier participants were unaffected. The researchers described the drop as similar to a 13-point dip in IQ, or the loss of a full night’s sleep.
The second set of experiments involved 464 sugarcane farmers in India who received most of their income once a year at harvest. The same farmers scored higher on cognitive tests after the harvest, when they had money, than before it, when money was scarce.
The authors argue that financial worry takes up what they call mental bandwidth, leaving less attention for everything else. They did not study food directly. But planning meals, comparing prices, cooking from scratch and resisting convenient options all draw on that same bandwidth, which suggests why diets may slip when money worries mount.
What it looks like in Australian households
Recent Australian data show how these pressures play out. The Foodbank Hunger Report 2025, based on an Ipsos survey of 4,260 adults conducted in June and July 2025 using a standard US Department of Agriculture questionnaire, found that 33% of Australian households, about 3.5 million, were food insecure. Of those, 61% were classed as severely affected.
The report found that almost half of severely food-insecure households had cut back on buying fresh produce, protein and other essentials, and almost one in three moderately food-insecure households had cut core items. Some severely affected households reported skipping meals or going whole days without eating. Single-parent households, households including someone with a disability or health condition, and renters were among the most affected.
Foodbank is a food relief charity, but its survey uses an established measure of food insecurity and a sample weighted to represent the national population.
What the research cannot say
These studies come from different countries, years and methods, and none of them follows the full chain from tight finances to worse health in the same people. The price studies measure what foods cost, not what people actually buy. The bandwidth experiments measure test performance, not shopping or cooking. And food prices and household budgets have changed considerably since some of this work was done.
Still, the findings point the same way. Healthier food tends to cost more for the calories it provides, money pressure appears to consume attention that good food choices require, and many households facing shortfalls report cutting back on exactly the foods nutrition guidelines recommend. On this evidence, poorer diets among people under financial strain reflect their circumstances, not simply their choices.
