According to a new study, an easy eating trick can save you the equivalent kilojoules of a Mars bar every day.

All you have to do is plan in advance and, ideally, buy your lunch straight after you've eaten breakfast.

Previous research has found that shopping for food when you’re hungry leads to unhealthier, more energy-dense choices.

“The body is always trying to defend its state and it makes very logical sense that if you're going for a period without food, and you're wanting food, you're more likely to go for the food that's high-calorie,” Endocrinologist Tony Goldstone from Imperial College London, told Reuters. 

“If we're needing energy, we're not going to go out for lettuce.”

Extending upon that understanding, the new study explored the food choices of 700 workers and 200 students who regularly ate at on-site canteens. The researchers, from the University of Pennsylvania, analysed more than 1000 lunch orders placed from 7am until right before participants ate lunch.

For every hour in advance that orders were placed, participants saved 160 kilojoules.

“Our results show that ordering meals when you're already hungry and ready to eat leads to an overall increase in the number of calories ordered, and suggest that by ordering meals in advance, the likelihood of making indulgent purchases is drastically reduced,” said lead author Eric Van Epps.

Interestingly, there was no difference in meal satisfaction between those who made an impulse purchase and those who made a healthier choice, suggesting that the healthier option is equally gratifying. The researchers also found that the participants made the healthier choices irrespective of what they ate for breakfast and not purposely trying to reduce kilojoules.

“These findings provide one more piece of evidence that decisions made in the heat of the moment are not as far-sighted as those made in advance,” said co-author, George Loewenstein.

“For example, people who plan to practice safe sex often fail to do so when caught up in the act, and people who, in dispassionate moments, recognise the stupidity of road rage nevertheless regularly succumb to it. Unfortunately, pre-commitment strategies are more feasible when it comes to diet than to many other 'hot' behaviours.”

Another way to curb your appetite is to drink up, according to another new study.

After controlling for other factors, the researchers from the University of Michigan found that people who weren't well hydrated were 1.59 times more likely to be overweight or obese.

“What we found was that people who were inadequately hydrated had increased odds of being obese,” study author Tammy Chang told NPR.

How do you know if you are well-hydrated, with water, of course?

“If your urine is light – almost like the colour of water – then you're probably well-hydrated,” Chang said.

Are you guilty of shopping hungry? Let us know in the comments below.

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