Yahoo Lifestyle The truth about your belly fat
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You know what insulin is. Well, sort of. But it’s worth knowing more...
WH takes a look at its dysfunctional relationship with abdominal fat, heart disease and cancer, and shows you how to use this knowledge to live a long, healthy life – with a flatter stomach.
Belly fat
It stops us from sitting down easily in skinny jeans, and leads us to stuff our bottom drawers with Spanx. But it can also indicate a bigger problem.
According to the Department of Health and Ageing, a waist circumference of more than 80cm for women (94cm for men) increases the risk of “lifestyle-related chronic diseases” like metabolic syndrome (or “Syndrome X”), type 2 diabetes, cardiovascular disease and some cancers.
And at the centre of it all is insulin – a normally helpful hormone that allows our cells to get energy from food. If your body becomes resistant to insulin things can go, well, apple-shaped. But even if you’re healthier than Gwyneth on a health kick, you can benefit from knowing more about insulin and how it works in your body.
The cells in your body need two forms of fuel, says Dr Ginni Mansberg, WH health expert and GP. “One is oxygen, which makes its own way into the cells. The other is glucose.” This is our chief source of energy and it comes from carbohydrates in food (take that, Dr Atkins).
“Glucose can’t make its own way into any cell,” Dr Mansberg says. “There’s a lock. Insulin, made by the pancreas, opens this lock and allows glucose into cells.” In a word, insulin is vital. It lets us work, exercise, have sex and dance to Kylie while vacuuming (er, but not at the same time).
Here’s how it works: when you eat, your blood glucose level rises, sending a memo to the pancreas to start pumping out insulin. The insulin then regulates how much glucose our cells get – some for that muscle, a bit for those fat cells – and also determines how much glucose to store as glycogen in the liver. (Glycogen is a molecule that will be converted back to glucose for energy later.)
Once glucose levels in the blood drop back to normal, the pancreas gets a message to switch off insulin production. Ideally, “normal” blood glucose levels when you haven’t eaten for hours are between 4 and 6 mmol/L (millimoles per litre); the level after eating is generally between 6 and 8 mmol/L, says Lyn Curtis from Diabetes Australia. “But for some people this may be too low, so target blood glucose levels should be individualised.”
When your blood sugar is really low – say you’ve gone for a long time between eating – the pancreas sends the hormone glucagon into the bloodstream, signalling the liver to break down stored glycogen into glucose. The glucose enters the blood and your blood glucose level increases to its happy set point, and insulin get to do its unlocking-the-doors-to-cells thing again.
If you overdose on high-GI foods and carbs, this puts immense pressure on your pancreas to pump out loads of insulin, says Dr Alan Barclay, spokesperson for the Dietitians Association of Australia. In response, the locks – actually receptors on the cells – shut down, resisting the insulin. So the pancreas sends out more insulin to get the job done.
Over time, this spells bad news.
Insulin overload
Too many episodes of feasting on high-GI foods (causing spikes and drops in blood sugar and excess insulin) can lead to insulin resistance, where excess insulin and blood sugar build up in the bloodstream, muscles don’t get the energy they need and the glucose winds up in the liver – where it’s converted to fat. Hello muffin top.
“Women with insulin resistance often tell me they’re eating salad and doing lots of exercise, but they can’t shift the weight,” says Dr Mansberg. “They feel this unbelievable tiredness mid-morning or mid-afternoon, because the sugar’s not making its way into cells.”
Not ideal, but it’s not the worst-case scenario. Insulin resistance is a precursor to type 2 diabetes (it used to be called “pre-diabetes”). “Insulin resistant people have a 50 per cent chance of developing diabetes within 10 years,” says Dr Mansberg. Researchers at Kyushu University in Fukuoka, Japan, also found that people with insulin resistance have a higher risk of developing brain plaques associated with Alzheimer’s disease. Eek.
The Australian Diabetes Council says that 80 to 90 per cent of people diagnosed with type 2 diabetes are overweight or obese, while the Australian Bureau of Statistics has reported a correlation between our increasing obesity rates and the prevalence of type 2 diabetes.
Genetics plays a big part in all of this, so the experts aren’t quite certain what comes first: the chicken (weight gain) or the egg (insulin resistance). The term “lifestyle condition” is bandied about, suggesting inactivity and processed food is to blame.
“We eat too much refined, processed food, with too many kilojoules relative to the activity we do,” says Dr Barclay. “That’s why diabetes rates start to go up in the mid 40s, after years of a poor lifestyle.”
Dr Mansberg says to diagnose metabolic syndrome, a patient needs a large waist circumference (more than 80cm for women), with any two of the following: insulin resistance; low HDL cholesterol (the good cholesterol); high triglyceride levels and high blood pressure (BP).
Think you might be at risk? An oral glucose tolerance test (OGTT) – you’ll need to fast overnight – by your GP will reveal if insulin is doing its job in delivering glucose to your cells, while checking those cholesterol and triglyceride levels. Your doc is likely to order a liver function test, which may indicate nasty visceral fat on the liver.
Be GI Jane
The good news is, unlike a post-schoolies unicorn tattoo, insulin resistance is completely reversible. And preventable. In fact, knowing more about how insulin works won’t just help you stay healthy, it can help stave off stomach chub too.
A low-GI diet is key to controlling your insulin and blood sugar levels. “Glycaemic Index refers to how your body responds to the carbohydrates in food,” says Caitlin Reid, dietitian, exercise physiologist and author of Health & The City.
Wholegrain cereals, legumes, lentils, nuts, seeds, dairy and most fresh fruit and vegies are all low-GI (for a full GI database, click on glycemicindex.com). “White or wholemeal bread, for example, is quickly digested and absorbed into the bloodstream, so we call it high-GI. Your blood sugar level spikes. But if you eat a low-GI food, such as grainy bread, it’s digested very slowly and not as much insulin is secreted.”
Good to know, whether you’re insulin resistant or not: one recent study by Penn State University, US, compared how much stomach fat people lost when they ate whole grains instead of refined grains. The wholegrain eaters lost 2.4 times more fat.
Related: Your perfect insulin-friendly day: get our eating plan
Amazingly, combining a high-GI food with a low-GI food will reduce the overall GI of your meal. But if you want to lose weight, don’t go piling (low-GI) cheese onto your white rice risotto just yet.
“You can’t only take GI into account; you need to consider kilojoules,” says Professor Stephen Colagiuri from the Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders at the University of Sydney. “Once you’ve reduced your kilojoules, eat lower GI foods to help your insulin levels,” he advises. “Also, there was a study in the New England Journal of Medicine recently that showed consuming low-GI with increased protein was better for keeping the weight off.”
So add a poached egg to your rye toast tomorrow morning.
Muscle vs fat
Another way to get insulin onside: strength training. Muscle is more sensitive to insulin than fat and most other organs. That is, the locks on muscle cells are opened more easily by insulin, as muscle is highly dependent on glucose for fuel. So if you have a low muscle mass, you’re more susceptible to insulin resistance... and if that happens, things get really tricky. “When you become insulin resistant, this relationship flips around: muscles become less sensitive to insulin and fat cells become more sensitive to insulin,” says Dr Barclay. It’s a vicious circle: the more fat you pile on, the more insulin resistant your muscles become. Gulp.
Best way to keep your muscle mass up and banish stomach fat? Interval training, incorporating weights, reckons Reid. “Do two to three resistance training sessions a week; the more muscle mass you have, the more sugar will be taken up,” she says.
As for how long you should exercise, if you want to lose some lard Dr Mansberg and Reid both say the recommended 30 minutes most days of the week isn’t enough (sorry). That’s the minimum for general health and weight maintenance, but for weight loss, “you need to do 60 to 90 minutes of aerobic exercise a day. If you need to break it up, that’s OK,” says Reid.
Another thing to break up is your sitting time. “When we sit we actually turn off our fat-burning enzymes, which also affect cholesterol and blood sugar levels. The people who do their 40 minutes at the gym but sit at a desk for 12 hours are still at risk (of chronic diseases),” says Reid. In short, sit less, move more and move often!
“You’ve got to get a pedometer,” says Dr Mansberg. “Take 10,000 steps a day.” And that’s on top of cardio and resistance, she adds. Sure enough, in a five-year study of 592 people published in the British Medical Journal, sedentary people who increased their steps to 10,000 per day improved their insulin sensitivity by three times.
We’ve heard countless times that a lack of shut-eye can affect weight, but skipping sleep can interfere with your insulin sensitivity – even in the short term. In a small study published in the Journal of Clinical Endocrinology & Metabolism, insulin sensitivity was measured after participants slept for eight hours, then after four hours. Researchers noted evidence of insulin resistance after just one night of little sleep.
“There is definitely an association between diabetes and a lack of sleep,” says Dr Barclay. “But if you’re awake all night with a newborn or suffering from a short-term lack of sleep, I wouldn’t worry. It’s not going to pose a serious risk until you’re in your mid-40s.”
For now, cut stress, get more sleep, stock the fridge with low-GI goodies and get moving – whether you’re insulin resistant or not. Your stomach will shrink, your GP will love you and you’ll never have to wear Bridget Jones pants again. Hurray!
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