Friday, September 03, 2010

Genetic excuse for obesity 'is a myth'?

There's actually nothing new in the research below. That you can work off fat by exercising hard and regularly is no news at all. There is no denial below that some people are genetically predisposed to fat

Obesity researchers have dismissed as a "myth" the excuse that we are "slaves" to our genes. Academics found that people could work off around 40 per cent of the extra weight that "fat genes" laid on them by exercising.

Although some people do have a predisposition to be overweight or even obese, scientists at the Medical Research Council's Epidemiology Unit in Cambridge discovered that having an active lifestyle could go a long way to countering a person's genetic inheritance.

The researchers made their conclusions after analysing the genes of over 20,000 men and women aged 39 to 79, looking for 12 genetic markers known to increase body mass index (BMI) and the risk of obesity.

With this, they calculated a "genetic predisposition score" for each person. They then asked them to fill out questionnaires about their physical activity levels at work and elsewhere.

They concluded: "The findings challenge the popular myth that obesity is unavoidable if it runs in the family and could guide future treatments to combat the obesity crisis."

Dr Ruth Loos from the MRC, who led the study, said: "Our research proves that even those who have the highest risk of obesity from their genes can improve their health by taking some form of daily physical activity."

She added: "People don’t have to run marathons to make a difference either - walking the dog or working in the garden all counts. It goes to show we’re not complete slaves to our genetic make-up and really can make a big difference to our future health by changing our behaviour. "It goes to show we’re not complete slaves to our genetic make-up and really can make a big difference to our future health by changing our behaviour."

The research is published in the journal PLoS Medicine.


Mental “exercise” linked to MORE dementia

An epidemiological study with some odd results. A proper double blind study would be needed to sort it out but the benefit of "mental excercise" is looking dubious. The authors can it all "post hoc" but that proves nothing.

Abstract here. I note that there seem to have been a lot of variables not controlled for -- IQ, education, general physical health etc. That makes any interpretation highly speculative

While staying mentally active in old age has been linked to a delayed onset of dementia, seniors who engage in such brain "exercise" may actually have a faster rate of decline once Alzheimer's is diagnosed, researchers reported Wednesday.

The current study, led by Dr. Robert S. Wilson of Rush University in Chicago, included 1,157 older adults who were dementia-free at the outset and were evaluated for cognitive decline over roughly six years.

At the study's start, participants reported on how often they engaged in a number of activities that were considered mentally stimulating — including reading, doing crosswords or other puzzles, playing games like cards or checkers, watching TV, listening to the radio and going to museums.

During the study period, 614 participants remained cognitively healthy, while 395 developed mild impairment in their thinking abilities, and 148 were diagnosed with Alzheimer's disease.

Wilson's team found that among the group who remained healthy, those who reported a greater number of cognitive activities showed a slower rate of decline in cognitive tests over six years. Test scores remained essentially unchanged among those in the top 10 percent for cognitive activities, but showed a gradual dip among those in the bottom 10 percent.

In contrast, among study participants who were diagnosed with Alzheimer's, those who were the most mentally active at the study's outset showed a quicker rate of decline over time than those who had been the least mentally engaged.

However, Hall pointed out that the key limitation of this and past studies on the issue is that they are observational studies. That is, they can show an association between mental activities and dementia onset and progression, but cannot prove cause-and-effect.

"The evidence from observational studies suggests that cognitive activities might delay the onset of dementia," Hall said, "but that has to be confirmed in intervention studies."

In an intervention-type study, participants would, for example, be randomly assigned to regularly perform some sort of mentally stimulating activity and then have their cognitive health followed over time and compared with that of a similar group who did not perform the activity.

If staying mentally active does delay dementia onset, evidence so far suggests the benefit would be modest.

In a study Hall and his colleagues published last year, they found that of older adults who developed dementia during the study period, the most mentally active ones were typically diagnosed just over a year later than the least mentally active men and women.

People in the most active group typically reported 11 "activity days" per week -- meaning, for example, they performed one activity, such as reading, writing or playing games, on all days of the week, and a second activity on four days of the week. The least active group reported four activity days per week.

"This doesn't prevent dementia. This doesn't prevent the (brain) pathology," Hall said. However, he added, if mental activities were found to delay dementia symptoms, or the need for nursing home care, by even a year, that would have a "tremendous public health impact."


1 comment:

John A said...

Academics found that people could work off around 40 per cent of the extra weight that "fat genes" laid on them by exercising.

Didn't the many famines over thousands of years show this? Prisons/dungeons? Bergen-Belsen? Eat less than necessary to maintain, work despite that, and your body will start to eat itself (or just plain die off, bit by bit) in the absence of sufficiency let be surplus.

And yes, either the reporter or editor[s] got carried away with the "myth" thing. I'd bet on editorial staff, since the body of the article makes it clear that weight loss is possible despite genetic pre-disposition.