Sneaky things that are making you fat
A SOBERING documentary has revealed the five things that can affect your weight - without you even realising.
BBC One's The Truth About Obesity looks beyond dieting to the other factors that could dramatically affect your weight.
Here are the top five.
TIME OF THE DAY
The later we eat, the more likely we are to gain weight.
This is not because we're less active - as commonly believed - but is down to our internal body clocks.
Obesity expert Dr James Brown said: "The body is set-up to handle calories much more efficiently during the daytime period when it's light than it is at night when it's dark."
This means that shift workers and those who do erratic hours may find it easier to put on weight.
At night, our bodies have difficulty digesting fats and sugars.
Eating before 7pm can help you lose weight or prevent you from gaining it in the first place.
Professor Tim Spector has been tracking the progress of twins Gillian and Jackie for 25 years through the Twins Research Study.
He believes that their 38kg weight difference could lie in the tiny organisms - microbes - that live deep in the gut.
He says: "Every time you eat anything, you're feeding a hundred trillion microbes. You're never dining alone."
Professor Spector believes increasing fibre in the diet can create diversity - and therefore help people lose weight.
After finding the pattern in a study of 5000 people, he concluded: "The greater the diversity, the skinnier the person. If you're carrying too much weight, your microbes aren't as diverse as they should be."
Sources of fibre include wholegrain cereals, fruit, vegetables, pulses and nuts.
Scientists at Cambridge University believe 40 to 70 per cent of the effect on our weight is down to the variation in our inherited genes.
Genes can affect appetite, the amount of food people want to eat, and the type of food we prefer.
They also have an impact on how we burn calories and whether our bodies can efficiently handle fat.
One of the 100 weight-affecting genes is called MC4R.
One in every 1000 people carries a defective version of this gene, which works in the brain to control hunger and appetite.
If you have a defective gene, it could make you more hungry and crave higher fat foods.
Professor Sadaf Farooqi said: "There's not really anything you can do about your genes, but for some people, knowing that genes may increase their chances of gaining weight can help them to deal with changes in diet and exercise."
TRICKING YOUR BRAIN
The Behavioural Insights Team suggests Britons are bad at keeping track of how much they eat, and that calorie consumption is being underestimated by 30 to 50 per cent as a result.
Behavioural scientist Hugo Harper suggests subconsciously changing your eating behaviour rather than relying on calorie counting could do the trick.
Dr Harper suggests moving unhealthy snacks out of sight - and putting healthy snacks out instead.
Swapping your favourite foods and drinks for lower-calorie alternatives can also work better than going cold turkey.
He also recommends reducing portion sizes - subconsciously it could be less hard work than using your conscious willpower.
Smaller plates can also stop you from overeating, he said.
Our appetites are controlled by our hormones and it has been discovered that bariatric surgery - the most effective treatment of obesity - makes the hormones that make us feel full increase and the ones that make us feel hungry drop in number.
The major operation involves reducing the size of the stomach by up to 90 per cent and is only carried out on people with a BMI of at least 35.
But researchers at Imperial College London have recreated the gut hormones that cause appetite changes after bariatric surgery and are using this for a new clinical trial.
Patients are given a mixture of three hormones every day for four weeks - and can lose between 2 to 8kg in just 28 days.
If the drug is proven safe, the plan is to use it until the patients reach a healthy weight.