Avoid going to the supermarket when you're very hungry, as you're more
likely to buy unhealthy food like crisps and sweets.
That's the health message of US researchers, who have looked at
whether fasting has an impact on food choices.
In an experiment, people who fasted for five hours before shopping
tended to buy higher-calorie food than when full.
The study has health implications, given the rise in extreme dieting,
says a Cornell University team.
Past research has suggested, perhaps not surprisingly, that people buy
and eat more food when they have been fasting or dieting.
However, the Cornell scientists wanted to find out whether fasting
affected what people buy, as well as how much.
They devised an experiment in which 68 paid participants were asked to
avoid eating for five hours, then shop online in a simulated grocery store for
high calorie and low calorie foods, including dairy products, snacks and meat.
Each high calorie item (including sweets, crisps and red meat) was
displayed alongside a similar low calorie item (such as fruit, vegetables and
chicken breasts), but prices were not included.
In half of the sessions, participants were first given a plate of
crackers to eat until they no longer felt hungry.
Shift in choices
In a second study, people were tracked while they shopped in a
supermarket, either after lunch, when they were full, or before supper, when
they were hungry.
The results showed that hungry people chose a higher number of high
calorie foods but there was little difference in the total number of food
products selected.
In other words, people who shop when they are hungry buy fewer low
calorie foods as a proportion of their food purchases but they don't buy more
overall.
The study has public health connotations, because fasting, for
religious reasons, to lose weight or due to busy lifestyles, is common, say
Prof Brian Wansink and Dr Aner Tal.
"Given the prevalence of short-term food deprivation, this has
important health implications."
Prof Walsink says one of the key messages for consumers is that doing
your weekly food shop on an empty stomach - perhaps late afternoon rather than
early afternoon - can have a big impact on healthy eating.
"One decision to shop hungry pretty much messes you up for the
rest of the week," he told BBC News.
"Any time you go shopping, make sure you grab an apple to eat on
the way
