Science: Nowadays the fats really do add up

More and more of us are becoming overweight, yet nobody is sure why. A new report helps dispel the myths.

Fat is an alarming issue. A fifth of men and women in this country are clinically obese. A further 45 per cent of men and 33 per cent of women are overweight. As a nation we are less obese than America, Australia, and Eastern Europe, but fatter than the Scandinavians and Japanese. Over the past 20 years there has been a rapid increase in obesity in developing countries. The health risks are high: an increase in 10 kilos results in a 20 per cent increase in the risk of premature death, and a 30 per cent increased risk of contracting diabetes.

These statistics prompted the British Nutrition Foundation (BNF) to commission a report on obesity, published today. It contains the most up-to-date research by a task force made up of the country's leading experts, chaired by John Garrow, formally professor of human nutrition at St Bartholomew's Medical College, London.

The report dispels a number of "fat myths". Many of us are aware that the more you eat, and the less energy you expend, the fatter you become. As the report says: "One of the few statements about obesity that can be made with absolute certainty is that obesity can only occur when energy intake remains higher than energy expenditure, for an extended period of time."

At the root of the problem is the fact that we have grown increasingly inactive; although we eat about 750 fewer calories a day than 20 years ago, we expend about 800 fewer calories. However, the trouble with fat, as anyone who has tried to diet knows, is that it's difficult to shift. It's not always that easy to tell exactly how much excess fat we are carrying. Many gyms and health centres do offer to measure fat content, but their methods are somewhat inaccurate, and the best (using infrared scanners) can assess our body fat only to the nearest kilo.

The report suggests using the body mass index (BMI) to check whether an individual is clinically obese. The one drawback is that it doesn't assess the proportions of lean tissue and fat, and may therefore misrepresent athletes' BMI since they have such a high muscle-to-fat ratio.

BMI is calculated by weight in kilos divided by height in metres squared. A BMI between 20 and 25 is normal, between 25 and 30 is overweight, and above 30 is clinically obese. Recent research indicates that an individual's waist measurement is a good indicator: statistically there is a health risk in a waist size greater than 94cm (34in) in men, and 80cm (32in) in women.

There is evidence to suggest that obesity levels are genetically inherited. Identical twins who are brought up apart tend to weigh a similar amount; adopted children also have similar fat levels to their biological parents, but not to their adoptive ones. The likelihood of inheriting the same position of body fat as your parents - big thighs or a pot belly - is between 18 and 50 per cent. However, a number of other factors, including environment, lifestyle and mental outlook, can interact with a person's genetic propensity to put on weight.

It is a myth that most thin people have a shrew-like metabolic rate and can eat enormous meals. Not all slim people spend their lives in the gym, but they could burn fat by constant fidgeting. Research conducted on the Pima Indians showed that fidgeting ran in the family, and a lack of it was correlated with a predisposition to obesity in later life.

In fact, overweight people have higher metabolic rates than people of normal weight. This is partly because of bigger mass - someone who weighs 40kg too much is lugging around the equivalent of two suitcases - and partly because weight gain is not entirely fat. About a quarter is extra musculature to support the bulk, and intestinal and liver tissue also increase; all these are more calorie-hungry than fat.

Most adults possess about half a billion mature fat cells. The number that are full of fat at any one time changes both minute by minute, and on a more long-term basis. Brown fat cells were once all the rage; any one who was Twiggy-thin was presumed to have a lot of brown fat. We now know that these cells (brown adipose tissue, or BAT) are largely found in animals where they are involved in regulating heat, and can influence obesity in rats, but the report suggests that they play only a minor role in human physiology.

The deposition of normal, or white fat cells, is influenced by gender and genetics. Women tend to have more fat deposits on their hips and thighs, for example, which are believed to provide some of the energy for breast- feeding. It used to be thought that the number of fat cells laid down in infancy would be the amount you had for life. According to the report, this is untrue. In one study conducted more than 20 years ago, 28 obese women lost 13 (out of a total of 38) kg of fat over 26 weeks. Their fat cells shrank, but only 2 per cent of them disappeared.

Recent research confirms this: once the number of fat cells a person has been born with are full, more are produced, and although in theory these fat cells can be killed, in practice it is rare. The purpose of a fat cell is to store fat, thus if someone has a large number of fat cells (even if some are empty), they will be predisposed to gain weight. This may be one reason why people who have initially lost weight put it back on. Even removing fat cells by drastic surgical measures, such as liposuction, does not help in the long term as immature fat cells can subsequently develop into mature cells to replace them.

The report claims that anti-obesity drugs may help: "Drugs will be useful to the extent that they make lifestyle changes easier to achieve, provided that they are cost-effective and safe." According to Professor Peter Kopelman, from St Bartholomew's and the Royal London School of Medicine and Dentistry, Sibutramine can be effective and has, as yet, not proved to be as harmful as other drugs on the market. It acts on the nervous system by preventing hormones - serotonin and noradrenaline - from being taken up the brain, and combats hunger pangs.

Sibutramine can lead to a 10 per cent reduction in body weight in three months. However, drug use is not a miracle cure and Professor Kopelman recommends this strategy only for those with a BMI greater than 30, who have already attempted to alter their lifestyle and diet. The side-effects of Sibutramine include nausea, insomnia, dry mouth, constipation and an increase in blood pressure and heart rate.

The stark truth is that the only way to maintain weight is to eat sensibly and exercise regularly (at least half an hour of brisk walking five times a week); losing a kilo of fat a week means eating 1,000 fewer calories every day. It may be tough, but in the end a healthy lifestyle is the only effective way to keep trim.

'Obesity: Report of the British Nutrition Foundation's Task Force', pounds 29.99, is available from the British Nutrition Foundation, 52-54 High Holborn, London, WC1V 6RQ www.nutrition.org.uk

Arts and Entertainment
'The Great British Bake Off' showcases food at its most sumptuous
tvReview: Bread-making skills of the Bake Off hopefuls put to the test
Arts and Entertainment
Eye of the beholder? 'Concrete lasagne' Preston bus station
architecture
Arts and Entertainment
Cliff Richard performs at the Ziggo Dome in Amsterdam on 17 May 2014

music
Arts and Entertainment

TV
Arts and Entertainment
Educating the East End returns to Channel 4 this autumn

TV
PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
Arts and Entertainment
The eyes have it: Kate Bush

music
Arts and Entertainment
From left to right: Mark Crown, DJ Locksmith and Amir Amor of Rudimental performing on stage during day one of the Wireless Festival at Perry Park, Birmingham

music
Arts and Entertainment

books
Arts and Entertainment
Tim Vine has won the funniest joke award at the Edinburgh Festival 2014

Edinburgh
Arts and Entertainment
Peter Capaldi and Chris Addison star in political comedy The Thick of IT

TV
Arts and Entertainment
Judy Murray said she

TV
Arts and Entertainment
Tim Vine has won the funniest joke award at the Edinburgh Festival 2014

edinburgh
Arts and Entertainment
Jeremy Paxman has admitted he is a 'one-nation Tory' and complained that Newsnight is made by idealistic '13-year-olds' who foolishly think they can 'change the world'.

Edinburgh
Arts and Entertainment
Seoul singer G-Dragon could lead the invasion as South Korea has its sights set on Western markets
music
Arts and Entertainment
Gary Lineker at the UK Premiere of 'The Hunger Games: Catching Fire'
tv
Arts and Entertainment
Christian Bale as Batman in a scene from
film
Arts and Entertainment
Johhny Cash in 1969
musicDyess Colony, where singer grew up in Depression-era Arkansas, opens to the public
Arts and Entertainment
Army dreamers: Randy Couture, Sylvester Stallone, Dolph Lundgren and Jason Statham
film
Arts and Entertainment
The Great British Bake Off 2014 contestants
tvReview: It's not going to set the comedy world alight but it's a gentle evening watch
Arts and Entertainment
Umar Ahmed and Kiran Sonia Sawar in ‘My Name Is...’
Theatre
Arts and Entertainment
This year's Big Brother champion Helen Wood
arts + ents
Arts and Entertainment
Full company in Ustinov's Studio's Bad Jews
Theatre
Arts and Entertainment
Harari Guido photographed Kate Bush over the course of 11 years
Music
Arts and Entertainment
Reviews have not been good for Jonathan Liebesman’s take on the much loved eighties cartoon
Film

A The film has amassed an estimated $28.7 million in its opening weekend

Arts and Entertainment
Untwitterably yours: Singer Morrissey has said he doesn't have a twitter account
Music

A statement was published on his fansite, True To You, following release of new album

Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    Middle East crisis: We know all too much about the cruelty of Isis – but all too little about who they are

    We know all too much about the cruelty of Isis – but all too little about who they are

    Now Obama has seen the next US reporter to be threatened with beheading, will he blink, asks Robert Fisk
    Neanderthals lived alongside humans for centuries, latest study shows

    Final resting place of our Neanderthal neighbours revealed

    Bones dated to 40,000 years ago show species may have died out in Belgium species co-existed
    Scottish independence: The new Scots who hold fate of the UK in their hands

    The new Scots who hold fate of the UK in their hands

    Scotland’s immigrants are as passionate about the future of their adopted nation as anyone else
    Britain's ugliest buildings: Which monstrosities should be nominated for the Dead Prize?

    Blight club: Britain's ugliest buildings

    Following the architect Cameron Sinclair's introduction of the Dead Prize, an award for ugly buildings, John Rentoul reflects on some of the biggest blots on the UK landscape
    eBay's enduring appeal: Online auction site is still the UK's most popular e-commerce retailer

    eBay's enduring appeal

    The online auction site is still the UK's most popular e-commerce site
    Culture Minister Ed Vaizey: ‘lack of ethnic minority and black faces on TV is weird’

    'Lack of ethnic minority and black faces on TV is weird'

    Culture Minister Ed Vaizey calls for immediate action to address the problem
    Artist Olafur Eliasson's latest large-scale works are inspired by the paintings of JMW Turner

    Magic circles: Artist Olafur Eliasson

    Eliasson's works will go alongside a new exhibition of JMW Turner at Tate Britain. He tells Jay Merrick why the paintings of his hero are ripe for reinvention
    Josephine Dickinson: 'A cochlear implant helped me to discover a new world of sound'

    Josephine Dickinson: 'How I discovered a new world of sound'

    After going deaf as a child, musician and poet Josephine Dickinson made do with a hearing aid for five decades. Then she had a cochlear implant - and everything changed
    Greggs Google fail: Was the bakery's response to its logo mishap a stroke of marketing genius?

    Greggs gives lesson in crisis management

    After a mishap with their logo, high street staple Greggs went viral this week. But, as Simon Usborne discovers, their social media response was anything but half baked
    Matthew McConaughey has been singing the praises of bumbags (shame he doesn't know how to wear one)

    Matthew McConaughey sings the praises of bumbags

    Shame he doesn't know how to wear one. Harriet Walker explains the dos and don'ts of fanny packs
    7 best quadcopters and drones

    Flying fun: 7 best quadcopters and drones

    From state of the art devices with stabilised cameras to mini gadgets that can soar around the home, we take some flying objects for a spin
    Joey Barton: ‘I’ve been guilty of getting a bit irate’

    Joey Barton: ‘I’ve been guilty of getting a bit irate’

    The midfielder returned to the Premier League after two years last weekend. The controversial character had much to discuss after his first game back
    Andy Murray: I quit while I’m ahead too often

    Andy Murray: I quit while I’m ahead too often

    British No 1 knows his consistency as well as his fitness needs working on as he prepares for the US Open after a ‘very, very up and down’ year
    Ferguson: In the heartlands of America, a descent into madness

    A descent into madness in America's heartlands

    David Usborne arrived in Ferguson, Missouri to be greeted by a scene more redolent of Gaza and Afghanistan
    BBC’s filming of raid at Sir Cliff’s home ‘may be result of corruption’

    BBC faces corruption allegation over its Sir Cliff police raid coverage

    Reporter’s relationship with police under scrutiny as DG is summoned by MPs to explain extensive live broadcast of swoop on singer’s home