Team McCallum

R&D for Lifetime of Life

Walking v diabetes+.

Dr Terry Dwyer and colleagues have found that walking cuts the risk of diabetes in a study of 600 adults in Tasmania. While the team focussed on diabetes, the results suggest a protective effect against metabolic syndrome and cardiovascular disease.

Roughly 600 adults aged around 50 in 2000 were tracked for 5 years.  At the start, most were overweight or obese and as a whole, the group gained weight over the period.

The volunteers were fitted with pedometers for 2 days in 2000. One finding was that those with higher daily step counts at this start time ended with a better body mass index (BMI), better waist to hip ratio and better insulin sensitivity, compared to those less active.

After 5 years, the group wore pedometers for another 2 days. As a whole, the group gained weight and became less active.  However, one third stayed active or increased their steps in the period, and again these were the ones with better measures on BMI, waist-hip ratio and insulin sensitivity.

The following figures are for those walking 10,000 steps, which is about 5 miles or 8km.

For a person of average height, weight dropped was just under 3kg, or about 6lbs. This corresponds to a BMI reduction of 0.83kg/metre squared. Insulin sensitivity increased by about 12%, with men doing slightly better than women.

These results are all ‘dose-dependent’. In other words, walking less still resulted in some improvements.

When the researchers factored in BMI, the differences between those active and those not disappeared, so the team attributed the improvement to a cut in body fat.

The researchers were looking at diabetes, and the improvement in insulin sensitivity would result in a considerably reduced risk of the disease.

The figures also strongly suggest there would be an improvement in other diseases linked to BMI and larger waists, including high blood pressure, metabolic syndrome, cardiovascular disease and more.

The impact on the waist is interesting, since fat stored around the waist is linked to adiposopathy (sick fat), and this study suggests that walking is a way to burn ‘sick’ fat preferentially to ‘healthy’ fat, reducing the waist to hip ratio.

January 17, 2011 Posted by | Accelerometer, Activity, Adiposopathy - sick fat, Aging, BMI - body mass index, CVD - cardiovascular disease, Diabetes, Exercise, High blood pressure, Metabolic syndrome, Success, Waist circumference, Walking, Weight management | Leave a comment

Fat kids v teen heart risk.

A study in the UK has looked at over 5,200 children, to see whether being overweight at age 9-12 is associated with cardiovascular risk factors at age 15-16. It also investigated whether body mass index (BMI) is useful, or whether other measures are better.

Dr Debbie A Lawler and colleagues took measurements of BMI, waist circumference and fat/lean mass by dual energy x-rays at start point and end point. For 75% of the children, the start was before age 10.

At the end, at age 15-16, a wide range of risk markers associated with cardiovascular disease (CVD) were measured.

Different detailed results were found for boys and for girls. However, in general, those overweight at the start point were at higher risk  of factors linked to CVD. (The ‘overweight’ definition used was that of the International Obesity Task Force.)

The following risk factors were all predicted – high systolic blood pressure, high ‘bad’ LDL cholesterol, low ‘good’ HDL cholesterol, high triglycerides, high insulin in blood. BMI was linked to high fasting glucose levels in boys only, and risk for some of the others was worse in boys than girls.

Diastolic blood pressure at the end was not predicted by BMI at the start measurement.

Girls who went from overweight at the first point into the normal range by the end were found to have no more risk than those girls in the normal range at both times. However, boys who improved their weight status also improved their risk profile, but it remained poorer than those in the normal range at both times.

Finally, the team found that although BMI is much criticised, it was as good a predictor as the other two methods, even the very precise x-ray method. So BMI was validated as a simple and easy way to predict a child’s future health profile.

November 28, 2010 Posted by | BMI - body mass index, Child Health, Cholesterol, CVD - cardiovascular disease, Gender, Health, High blood pressure, Metabolic syndrome, Obesity, Success, Waist circumference, Weight management | Leave a comment

Exercise v diabetes.

Dr Timothy S Church reported in the Journal of the American Medical Association that a combination of resistance and aerobic exercise of around 140 minutes per week was successful in improving a key marker in type 2 diabetics already on medication.

262 sedentary men and women, average age 56, were randomly allocated to one of – a control group (no exercise), resistance training, aerobic training, and combined resistance and aerobic training.

The resistance training group exercised 3 times a week. The aerobic group did enough exercise to burn 12 kcal per kilo of bodyweight per week. The combined group did aerobics to expend 10 kcal per kilo per week plus 2 sessions of resistance training, which totalled around 140 minutes. This is fairly close to 2008 guidelines of 150 minutes of exercise per week.

The program ran for 9 months, and medicine continued to be used as prescribed by a physician.

Compared to controls, the other groups decreased waist circumference by around and inch. The resistance training group lost 3.1 lbs of fat, while the combination group lost 3.7 lbs of fat (both retaining lean tissue unchanged).

The key outcome measure was glycated hemoglobin (HbA1C). This is a measure of the long term average level of blood sugar.

While the resistance-only and aerobics-only groups had lower values of HbA1C than controls, these were not great enough to be statistically significant, so these forms of exercise on their own don’t have enough impact.

For the combined exercise group, the cut in HbA1C compared to controls was big enough to be significant. This supports the 2008 guidelines, that a mix of both at around 150 minutes per week is beneficial.

During the study, the control group increased its use of diabetic medicines, while in the combined exercise group the use of medication to treat diabetes dropped.

November 26, 2010 Posted by | Diabetes, Exercise, Success, Waist circumference, Weight management | Leave a comment

Vitamin D v genes?

A study in white males living in the US has concluded that vitamin D levels are 70% determined by genetics in winter but in summer this is replaced by environmental factors, such as sun exposure.

The research, published in the American Journal of Clinical Nutrition, was based on twins from the Vietnam Era Twins (VET) registry, one of the largest in the US, so the men had an average age of 55 when studied.

The men were followed over 12 months to find out the level of vitamin D in their blood in each month, to allow comparison to be drawn between the 6 months aggregated into ‘summer’ and the other 6 called ‘winter’.

Then a standard routine for determining the genetic component was used. Identical twins are assumed to be 100% identical genetically, while for non-identical twins this is 50%. Twins living together are assumed to have a 100% shared common environment, while  those living apart have a unique environment. Blend these into the results, and genetic and environmental components can be teased out.

The researchers from Brazil and the US found that, in general, people with lower blood levels of vitamin D had a larger body mass index, a larger waist-hip ratio (a marker for cardiovascular disease), a higher Framingham risk score (a marker for coronary artery disease) and a higher percentage were diabetic.

And when doing the twins analysis, they found that genetics dominate in winter (70%), but in summer this impact disappeared, and the determinants were environmental, with 53% due to shared environments and 47% due to unique environments.

The team noted other research has found that genetic factors appear to have much less influence in women.

They also raised an interesting point that they did not resolve. Other studies have found that in white people (but not in non-whites), vitamin D levels decrease the further north you live, due to less UVB in sunlight. However, the current team could not find this effect in their subjects, despite the fact that they ranged from 21 degrees N to 49 degrees N.

While the town of Uppsala in Sweden is 60 degrees N. The current study noted previous research in white twins, both male and female,  from Uppsala, which found things worked the opposite way around. That team reported that genetic factors were important in summer, at 48%, but in winter were replaced by a mix of shared and unique environments. Quite why Sweden appears to work in the opposite direction to the US was not explained.

November 19, 2010 Posted by | BMI - body mass index, CVD - cardiovascular disease, Diabetes, Genetics, Health, Vitamin D, Waist circumference | 1 Comment

Sugared drinks v diabetes.

Dr Frank B Hu and 5 colleagues in N America have found that sugar-sweetened drinks, even at a low level, are linked to an increased risk of type 2 diabetes and metabolic syndrome. This effect is independent of any impact the sweetened drinks have on weight or on total calorie consumption. Further, it kicks in at levels as low as 1 to 2 standard size drinks per day.

The research team combed medical literature for good quality studies, in order to combine them. They found 8 studies of sugar-sweetened drinks and type 2 diabetes, covering 311,000 people, and 3 studies for metabolic syndrome, covering nearly 20,000 people.

From these they calculated that 1 to 2 sweet drinks per day, compared to less than 1 per month, raised the risk of type 2 diabetes by 26% and metabolic syndrome by 20%. One drink was a standard 12 oz size in the US, which is slightly larger than the 330 ml size in Europe. They found the result was dose-dependent, so more soft drinks increased both risks.

They concluded “In addition to weight gain, higher consumption of sugar-sweetened beverages is associated with development of metabolic syndrome and type 2 diabetes.” 

The full research paper shows that the sweetening component has quite different effects depending on whether it is fructose, glucose or an artificial sweetener. However, in the form of an added sweetener at this magnitude all have undesirable health effects.

The paper also references other research to show that the preferred US sweetener, HFCS (high fructose corn syrup, a 55/45 mix of fructose and glucose) and the standard European sweetener (sucrose, a 50/50 mix of fructose to glucose) both increase the risk of metabolic syndrome and type 2 diabetes through not only weight gain but through other paths. These extra paths include increased dietary glycemic load leading to insulin resistance, beta-cell disruption and inflammation. Further problems are hypertension and an increase in visceral fat (bad fat).

These findings dovetail neatly with recent research that there are good carbs and bad carbs.That report is here.

As soft drinks increase visceral fat, and both increase the risk of type 2 diabetes, this may explain why US adults have larger waist sizes than their UK equivalents, and also twice the rate of diabetes. That report is here.

October 28, 2010 Posted by | Diabetes, Diet, Frank B Hu, Glycemic index, Health, HFCS - high-fructose corn syrup, Metabolic syndrome, Obesity, Soft drinks, Success, Sugar, UK, United States, Waist circumference, Weight management | Leave a comment

Waist v death.

Dr Eric J Jacobs reported on the link between waist circumference and all-cause mortality. The team followed over 100,000 men and women aged 50 plus for 10 years.

Jacobs found a larger waist was associated with higher mortality, independent of weight or body mass index (BMI).

Increased waist size led to increased deaths from respiratory disease, cardiovascular disease and cancer, plus increases in a list of non-fatal medical conditions.

The reason may be that a bigger waist is strongly correlated with fat deposited around the internal organs, which is thought to be more pathogenic than fat stored under the skin or on hips and thighs.

For men, every 10cm (4 inch) increase led to an increased risk of death of 16% at normal BMI (up to 25), 18% if overweight (BMI 25 to 30) and 21% if obese (BMI 30 plus).

For women, the corresponding increases were 25%, 15% and 13%. So women in the normal BMI range are particularly at risk from a larger waist.

August 10, 2010 Posted by | BMI - body mass index, Cancer, CVD - cardiovascular disease, Eric J Jacobs, Gender, Health, Obesity, Success, Waist circumference, Weight management | Leave a comment