Where we store fat can potentially have a powerful effect on our health. Photo / Getty Images
Where we store fat can potentially have a powerful effect on our health. Photo / Getty Images
Most of us know that being overweight or obese is associated with a host of health problems, including heart disease, cancer, Type 2 diabetes, high blood pressure, depression and dementia. But it's not just how much you weigh, but where in your body that you store that fat that counts.
And not all fat is created equal. Subcutaneous fat lies just under the skin – it's the inch you can pinch. This is the least worrying form, particularly if you don't have too much of it, says Dr Sarah Berry, an associate professor in nutritional sciences at King's College London and chief scientist at the health science company ZOE. The most toxic form of fat is the "visceral" or internal fat that accumulates deep in the upper body. This fat causes our waistlines to expand. But more sinisterly, says Dr Berry, "Visceral fat is 'metabolically active', which means it upregulates – or increases – production of chemicals that affect chronic diseases such as inflammation and Type 2 diabetes. In contrast, fat on the thighs and hips is less metabolically active and so more benign."
This is why researchers were surprised when a new study revealed that one type of thigh fat was linked to a greater risk of developing heart failure. And the link held true even if people were otherwise slim. The research was published online in the July issue of the journal JACC: Heart Failure. But before you start worrying too much about your curvy thighs, this risky fat wasn't the wobbly kind associated with cellulite, but fat that formed within leg muscles.
The researchers tracked 2399 people aged 70 to 79 years without heart failure for an average of 12 years. They found that people whose thigh muscles were most marbled with fat had a 34 per cent increased risk of developing heart failure compared to those who were least affected. Why? The researchers suggested that "intramuscular" fat, like belly fat, is inflammatory, alerting the immune system to attack the body.
So, given that where we store fat has such a potentially powerful effect on our health, what do your own lumps and bumps mean for your future? And what can you do to reduce your risks?
Abdominal fat
When it comes to storing fat, your middle is the riskiest spot, upping your risk of heart disease, stroke, cancer, Type 2 diabetes and even depression and dementia. People with an apple body shape at any age are considered at the highest risk for health issues compared to the other body types. A 2019 study of almost 160,000 women found that in post-menopausal women with a healthy BMI of less than 25 but "central obesity", defined as a waist-to-hip ratio 0.85 or larger (see box below) were between 13 per cent and 44 per cent more likely to die than women of the same age but with slimmer waists. They were even more at risk of heart disease and cancer than women who were obese but had comparatively smaller middles.
Why is fat around the middle so troublesome? This type of abdominal fat pours inflammatory chemicals into the bloodstream and can infiltrate organs. Fat cells in the liver can cause non-alcoholic fatty liver disease, which can permanently scar the organ and even cause cirrhosis. A new study published in the journal Neurology has found that people with fatty liver disease may have a higher risk of dementia. Fat can also invade the pancreas, causing Type 2 diabetes.
Most women are protected from abdominal obesity by their hormones – especially oestrogen, which directs fat to the hips and thighs. Dr Berry says, "This difference in body composition is why men have a higher risk of metabolic disease when compared to pre-menopausal women with a similar BMI."
However, this all changes at menopause when oestrogen levels drop. In a five-year study of women aged 46 to 57, the menopause appeared to trigger an increase in total body fat and especially abdominal (or visceral) fat. Women are at risk if their waist measures 35 inches or larger while men are at risk when their waist measures 40 inches or larger.
Hip-hip-hooray
You may not feel particularly blessed by your large bottom or full thighs but, if you are a woman, this is the healthiest place to store fat, as long as it's the cellulite kind just under your skin and not buried deep in your muscles. Why? It turns out that fat is not just inert padding, but is a different material depending on where it is stored. In 2013 researchers in the US found that belly fat has over a hundred genetic differences from the fat in your legs.
Lead researcher Dr Steven Smith, director of the Florida Hospital Sanford-Burnham Translational Research Institute for Metabolism and Diabetes, said, "We believe these genes actually programme those fat cells to respond differently to different hormones and other signals. Even though many women may hate having large hips and thighs, that pear shape actually reduces their risk of heart disease and diabetes. In fact, women who have heart attacks tend to have more belly fat than thigh fat."
What's more, a 2010 study found that when we gain weight in our legs, we make more fat cells, but when we gain weight around the waist, our fat cells simply expand. This is bad news because when fat cells get too big, excess fat starts to spill out into the bloodstream.
Subcutaneous fat lies just under the skin - it's the inch you can pinch - and this is the least worrying form. Photo / Getty Images
Fat around the neck
Your neck might be the last part of your body that you worry about, but a host of research indicates that, as your neck size grows, so does your risk of heart disease.
That's true for men and women and applies even if your waistline is still relatively trim. In 2009, researchers told the American Heart Association's annual meeting that data collected from 3,320 people showed that the bigger the neck, the more likely it was that the person had high levels of LDL (low-density lipoprotein) – or "bad" cholesterol – and blood fat, insulin resistance and high blood sugar. A recent study in the Journal of American Heart Health says that high neck circumference starts at 14 inches for women and 17 inches for men, and neck circumference was associated with a greater heart risk than would be expected according to more traditional measures like BMI.
But why is neck fat risky? Neck fat is a good marker for raised upper body fat, which pours free fatty acids into the bloodstream, increasing the risk of cardiovascular disease. Fat around the neck can also cause pressure on the airways during sleep, meaning that people may struggle to breathe during the night. This sleep apnoea is an independent risk factor for stroke, depression and high blood pressure.
A bountiful cleavage
In 2008, a study of more than 92,000 women found that a bigger bra cup size at age 20 could triple a woman's risk of being diagnosed with diabetes two decades later. Breast size can be associated with obesity but, even when the researchers at Harvard University and the University of Toronto looked at women with a slender BMI of 21 to 23, those who said they wore an A cup were three times less likely to develop Type 2 diabetes as those who wore a D cup or larger. A separate study in 2012 suggested that bigger breasts were not a risk factor in themselves, but could indicate that we're more predisposed to the active kind of visceral fat.
How to tackle body fat
While it's impossible to target fat "trouble spots", making healthy life changes can reduce your overall body fat, so you'll lose it from wherever it is stored.
Swap saturated fat for plant-based monounsaturated fat. This seems to prevent and reverse intramuscular fat, the kind in the new thigh study.
Eat more fibre. A 2011 study by researchers at Wake Forest Baptist Medical Centre in the US found that for every 10g increase in soluble fibre eaten per day, visceral fat was reduced by 3.7 per cent over five years. Soluble fibre can be found in fruit, vegetables, beans and lentils.
Be active. Exercising vigorously for 30 minutes, two to four times a week, resulted in a 7.4 per cent decrease in the rate of visceral fat accumulation over the same period.
Lose weight. A 2016 study found that people with Type 2 diabetes who lost 10 per cent of their weight had a 21 per cent lower risk of heart attacks and strokes.
Diabetes expert Professor Roy Taylor, director of Newcastle University's Magnetic Resonance Centre, says, "However much fat you may have in your body, the development of Type 2 diabetes is telling you that you have too much. As a rule of thumb, decreasing your body weight by 15kg (about 2st 5lb) will correct the excess fat whatever you currently weigh." This can potentially reverse diabetes entirely.
