We all know "eat a bit less, exercise a bit more" is the key to weight loss, but there are many other factors at play that are only now being discovered by scientists.
Last month US researchers revealed how morning sunshine can help us to slim. They found that people who had most of their daily exposure to moderately bright light in the morning had a lower body mass index (BMI) than those who had most of their light exposure later in the day.
This is because light sets our body clocks, which in turn control metabolism. When our body clocks are synchronised with the day we feel less hungry and our bodies use energy more efficiently, says the study author Phyllis Zee, professor of neurology at Northwestern University, Illinois.
But that's not the only unexpected way you can shed the kilos. Here are another 15 surprising slimming strategies.
1 Many of us eat out of habit, particularly when we are distracted by something else, such as television.
But doing something to break that habit, such as eating with the "wrong" hand (the left hand for right-handers and vice versa) can make a difference, say researchers from the University of Southern California.
The study of moviegoers, published in Personality and Social Psychology Bulletin, found that people ate only half as much popcorn if they were asked to eat it with their other hand.
2 Chillies can be hot stuff for losing weight, since they rev up your body's metabolism, making it burn more fat.
A month-long study of 78 people in the American Journal of Clinical Nutrition concluded that supplements containing a key substance in chilli, dihydrocapsiate (DHC), can raise the metabolic rate.
Angelo Tremblay, of Laval University in Canada, believes that capsaicin, a compound in jalapeņo and cayenne peppers, may increase the release of stress hormones, which can speed up metabolism.
His research shows that the heat may reduce the appetite - and he found that a teaspoonful of pepper (capsicum) before meals reduced the amount people ate.
3 There seems to be a similar benefit with olive oil. Fatty acids in it can make your body burn food faster, according to a study by dietitians at McGill University in Quebec. The beneficial effect was still working six hours after volunteers had a breakfast drizzled with olive oil.
4 Restaurants, with all their clanging noises, make us want to eat sweeter and saltier foods, according to research in the journal Food Quality and Preference.
Our nervous systems are wired to respond to loud noise with a faster heartbeat and higher blood pressure, so that we are ready to flee from danger.
In noisy restaurants we respond by eating faster and drinking more alcohol, says research by Dr Adrian North, a psychologist at the University of Leicester.
5 Clenching your fists for half a minute can halt temptation when you have a food craving, reported the Journal of Consumer Research in 2011. The researcher, Iris Hung, says we subliminally associate flexed muscles with endurance and can use this link to bolster our willpower.
6 Apple peel contains ursolic acid, which increases muscle and levels of brown fat (found in the neck and between the shoulder blades).
Both of these boost the rate at which our bodies burn calories.
7 Eating a breakfast that includes a sweet dessert may help you to lose weight, say researchers from Tel Aviv University in Israel.
Their study, published in 2012, found that dieters who followed this regimen lost more weight over eight months than those on the same calories but who had a smaller, low-carb breakfast.
The key is to indulge in the morning, when the metabolism is at its most active and we can work off the extra calories.
8 Our appetite is partly governed by a mechanism called sensory specific satiety. Basically, we feel fuller if we're eating only one food.
It is like eating a plate of meat and thinking you'd burst with one more forkful - then pudding arrives and you can eat it.
Nutrition scientist Barbara Rolls says variety in the form of colours makes you eat more and the greater the contrast in taste between the foods on your plate, the more you will eat.
9 Use tall, thin glasses for calorie-laden drinks such as alcohol and fruit juice, and squat glassware for healthy, calorie-free water.
A study published last year in the journal Substance Use and Misuse found we tend to pour at least 10 percent more wine into a wide glass than a standard one. "People have trouble assessing volumes," says Laura Smarandescu, professor of marketing at Iowa State University.
"People tend to drink less from a narrow glass, because they think they're drinking more."
Red wine can make a difference because we notice it more. Participants in the study poured 9 percent more white wine into a clear glass than when pouring red.
10 Thinking ahead can help you to avoid eating junk food. Scans show that hungry brains release hormones that make us crave high-fat, high-sugar foods.
Dr Alain Dagher, of the Montreal Neurological Institute, told a meeting of neurologists in 2011: "If you go to the supermarket hungry you are drawn to high-calorie food."
11 Your mother was right to tell you to chew each mouthful. A Japanese study of 4 700 people found fast eaters weigh on average 10kg more than slow chewers.
In the Journal of Epidemiology, the researchers also warned that eating too fast may raise the risk of diabetes.
Thirty women were given a large plate of pasta and when told to eat quickly they consumed 646 calories in nine minutes. When encouraged to pause between bites and chew each mouthful 15 to 20 times, they ate just 579 calories in 29 minutes.
The slow eaters said they enjoyed their food more.
12 Bigger forks can mean slimmer tummies. So says a 2011 study, which found that taking larger bites can lead to us eating less.
The reason, according to the Journal of Consumer Research, is that a large fork helps diners to notice how much of a dent they are making in their food.
13 Our idea of "normal" weight depends on the size of those around us. A long-term study in the US revealed that if someone has a friend of the same sex who becomes fat, their risk of being overweight doubles.
Being influenced by those around us in this way is called "social contagion". Research in the journal Obesity says it explains overweight families.
Denise Taylor, a Malvern-based psychologist who lost 20kg, says she adopted a "virtual" friend - the lithe singer Shakira. 'Whenever I wanted to eat cake, I'd ask myself: "What would Shakira do?" '
14 Use olive oil instead of butter on bread and you will eat 16 percent fewer calories and drop your bread consumption by a quarter, according to a study published in the International Journal of Obesity.
It is thought that olive oil stimulates taste receptors more powerfully than butter, making people feel fuller quicker.
15 Insufficient sleep knocks our appetite hormones out of kilter.
A Chicago University study that cut 12 young men's nightly sleep down to four hours found their levels of appetite hormone ghrelin rose by 28 percent after only two days.
Levels of leptin, which tells the brain the stomach is full, fell by 18 percent. They began to crave high-carb foods.