Weight may depend as much on when you eat as what, research suggests.
The body clock's effect on metabolism could be an overlooked factor driving obesity, say scientists.
New evidence from studies of mice suggests that 24-hour snacking, especially at night, can pile on the pounds.
Restricting eating to sensible meal times, on the other hand, may help fight the flab - even with big helpings.
Researchers compared mice fed the same amount of high-fat food round the clock or over a period of eight hours.
The mice given a restricted time in which to eat were protected against obesity, and also suffered less liver damage and inflammation.
Lead scientist Dr Satchidananda Panda, from the Salk Institute for Biological Studies in the US, pointed out that every organ has a "clock".
Livers, intestines and muscles worked at peak efficiency at certain times and were more or less sleeping at others.
These metabolic cycles were critical for a wide range of biological processes, from cholesterol breakdown to glucose production.
"When we eat randomly, those genes aren't on completely or off completely," said Dr Panda.
He added there was evidence that eating patterns had changed, with people having greater access to food and reasons to stay up late, for instance to watch TV. When people were awake, they tended to snack.
The timing of food consumption should be given more consideration by obesity experts, said Dr Panda.
"The focus has been on what people eat," he said. "We don't collect data on when people eat."
The research is published in the journal Cell Metabolism.
Take a look at other unusual things that make us put on weight...
Unlikely Things That Are Making You Fat
Research by psychotherapist Dawn Billings discovered that snooping at your partners phone or Facebook can lead to piling on the pounds. Billings claims that if you find something you didn't want to see, the stress of it all triggers the cortisol hormone, which interferes with the appetite-regulating hormone, letin. This can lead to an increase in hunger, making us lean towards emotional food binges.
Scientists from the <a href="http://www.mountsinai.org/" target="_hplink">Mount Sinai Medical Center</a> claim that phthalates, the chemicals found in 70% of cosmetics including shampoo, throw the body's weight control system off kilter. These chemicals are also linked to depressing testosterone levels in the body, which can increase the risk of weight gain
Recent research by the<a href="http://www.nia.nih.gov/" target="_hplink"> National Institute of Aging</a> found people who are highly emotional, organised and disciplined are more likely to be overweight. They also found that impulsive people have higher BMI's than those who are more relaxed and laid back.
Although its sole purpose is to disguise any unsightly lumps or bumps, it could give wearers a false sense of security, meaning they ditch diets as they know their pair of <a href="http://www.spanx.com/home/index.jsp" target="_hplink">Spanx</a> knickers will hold in their muffin top.
Those who guzzle diet fizzy drinks in the false hope that they're being healthier than drinking the full fat version, are still at risk of gaining weight. According to a study by the <a href="http://www.utexas.edu/" target="_hplink">University of Texas</a>, people who drink diet drinks see their waistbands expand 70% faster than those who drank normal fizzy drinks. This is because they believe they can drink more because of its lower calorie-count.
Falling in love can make you fat, research by the <a href="http://www.uconn.edu/" target="_hplink">University of Connecticut</a> has discovered. Otherwise known as the 'boyfriend layer', when a relationship becomes more established, couples tend to relax their fitness regime, eat out more - and eat more food. This is because new couples 'bond' over food and spend a lot of time doing sedentary things, like lounging on the sofa or in bed.
Women who are fed up at work are more likely to comfort eat, a study by the <a href="http://www.umassmed.edu/index.aspx" target="_hplink">University of Massachusetts Medical School</a> has found. Those who are hacked off with their everyday routine find comfort in 'emotional eating' when stressed and anxious rather than eating when hungry.
Lack of sleep disrupts the body's natural circadian pattern, which controls moods, alertness and appetite over a 24-hour period. If this is altered, it causes an imbalance in the leptin hormone (the hormone that tells us when we're full) and the ghrelin hormone (the hormone that tells us when we need food for energy). If these are out of control for regular periods, it can lead to weight gain.