The single most important factor in determining your resting metabolic rate (the amount of energy you utilise at rest) is how much lean muscle tissue you have. Your muscle tissue uses 16-22% of your daily calories just to exist. (Your liver uses 21% and your brain 20%, but you can't do much about beefing them up.) "Increasing metabolic rate through the development of more muscle tissue is the key to lasting weight loss," says Pete Williams, founder of London health club Health Dept. Resting muscle uses five times as many calories a kilogram a day as fat does. In an 18-week study from the University of Limburg in Holland, average daily metabolic rate increased by 9.5% and energy expenditure by 10% as a result of twice-weekly strength training. "But make sure your training is sufficiently challenging to increase muscle mass, by using weights that are heavy enough, and by training progressively and consistently," advises Williams.
Drink iced water
Here's a bit of maths to stoke your metabolism. It takes one calorie to raise the temperature of one litre of water by 1 degree. The body needs to heat water to body temperature (36.8C). The difference between the temperature of iced water and body temperature means you'll burn 36.8 calories "warming up" a litre of iced water. Supping two litres, therefore, is enough to burn off half a KitKat. At least, that's the theory. But don't go drinking gallons of icy water to help negate that piece of chocolate gateau you scoffed - there is such a thing as too much water.
Use your cycle
Not the two-wheeled one in the shed - your monthly one. "Basal metabolic rate (BMR) fluctuates throughout a woman's menstrual cycle," says Patricia Symonds, registered dietician and lecturer at Emory University, Atlanta. "BMR tends to be at its lowest a week before ovulation, and research has found an 8-16% rise in energy expenditure during the 14-day period following ovulation (the luteal phase)." A Penn State University study showed that, while women burn about 4% more calories a day during this time - they also consume 4% more calories. There is another way to make the most of the metabolic boost, though. Research from Ohio University shows that exercising in the luteal phase, when progesterone and oestrogen levels are high, burns more fat than at other times of the month.
Frontload your day
Metabolic rate is shaped like an ice-cream cone - highest in the morning, declining gradually through the day. Most of us, however, eat lightly in the morning and scoff larger meals as the day wears on, failing to take advantage of this daily peak. A study in the American Journal Of Clinical Nutrition revealed that starting the day with a meal boosted resting metabolic rate by 10%, while other research showed that people who skipped breakfast or lunch and ate most of their calories in their evening meal had lower metabolisms than "frontloaders."
Eat more protein
Ten per cent of the calories we consume each day are used up in digesting what we've eaten. It's called the thermic effect of food. "Contrary to popular belief, though, this doesn't mean that frequent small meals are more advantageous than one large meal," says Symonds. But meal content might increase your metabolism- because not all nutrients have the same thermic effect. Around 25-30% of the calories derived from protein are used up in its metabolism," says Symonds. Compare that to 6-8 of every 100 calories of carbohydrate and just 2-3 of every 100 fat calories, and ensure you have a serving of good quality protein at every meal.
A recent study at the Mayo Clinic in Minnesota found that one of the biggest determinants of who is overweight and who is skinny was their level of non-exercise activity thermogenesis (NEAT), better known as fidgeting or pottering. Obese subjects burned 350 calories a day fewer than leaner ones simply because they were more inert. While the leaner folk wiggled, stood, walked and constantly changed position, the overweight subjects sat more and fidgeted less.
Exercise more often
"Metabolic rate can increase as much as 15-fold during strenuous exercise," says Symonds. "And it doesn't return to normal the second you stop. In fact, the post-exercise elevation in metabolic rate (known as the afterburn) can make a significant contribution to overall daily energy expenditure." The more frequently you exercise the greater the afterburn effect - even if the overall volume is the same.