Research, published in PLOS Genetics, reports that the effects of a genetic predisposition to obesity can be decreased to by performing different kinds of exercise, to different extents.
Prof Steve Jones, Professor of Genetics, University College London (UCL), said:
“This paper shows, once again, that the more we learn about genetics the more we see the importance of the environment. Fifty years ago, China had almost no obese people; now it ranks just behind the United States in the number of overweight adults and comes top – or bottom – of the global tables for the number of obese children. Of course, the genes have not changed in that time, but China’s way of life has been transformed. Lots of poor-quality food means more fat people – but, as these researchers show, some of them are, because of their DNA, more at risk of the condition than are others. The authors – quite rightly – do not assume that the genes behind obesity in China are necessarily the same as in the West, but instead screen much of the DNA of the fat and the thin group among almost twenty thousand members of the Taiwan Biobank population, to search for consistent differences between them; and found plenty. The more of the obesity variants an individual had, the higher his or her risk of being overweight, as measured by waist size, body mass index, proportion of fat, and more. Before the days of cheap food, these genes were irrelevant, but today they may, given the effects of obesity on health, be lethal for some of their carriers.
“One way to get thin is to eat less (although dieting often does not work) but another is to burn more fuel. Some among the thin group carried lots of genes that might have pushed them towards obesity – but they exercise much more than others, with jogging the most effective way to keep the lard at bay, while fast walking and energetic dance or yoga also does something to help. That environmental shift has solved a genetic problem that damages those who sit idly at home (or indulge only in cycling, swimming and stretching, none of which do much to help lose weight).
“In the West, and perhaps also in Taiwan, several of the genes that predispose to fatness are active not in the gut, but in the brain. They alter the amount of food needed to satiate their bearers, so that in a society with lots of junk food those who carry them eat more before they put down their knives and forks. Many people find the idea of such inherited differences in behaviour disturbing or distasteful, but hunger is a good example. Differences in intelligence, too, are in part related to inherited variants – but, once again, the environment plays an important part. The children of high-IQ parents who live rich and varied lives have scores quite similar to those of their mother and father, but those of smart parents who live in poverty, with few books and not much stimulation, are much less like their parents, for their grim environments do not allow their favourable genes to manifest their effects.
“The question of nature and nurture is often seen as cutting a cake into a slice called gene, and another called environment. The Taiwan study shows how wrong this is; to separate the two would call for un-baking it to get back its ingredients – starch, sugar, and fat – and that would be impossible; but you can do that job by digesting it so that and, for some people, too many cakes, and a lazy life, makes them fat. A regular run will solve their problem; and even for those whose genes predispose them to be skinny, would probably do them a lot of good as well.
Prof Lora Heisler, Chair in Human Nutrition, Rowett Institute, University of Aberdeen, said:
“This study adds to the collection of emerging evidence of the benefits of physical exercise in reducing obesity in those of us with and without the genes that make it easier for us to gain weight.
“Thousands of adults in Taiwan volunteered a blood sample, physical examination and self-report of physical activity for the Taiwan Biobank (TWB). Kuo and colleagues tapped into this biobank to investigate the effect of genes and physical activity on degree of obesity in 18,242 adults. Similar to the UK, around half reported engaging in regular physical activity. Kuo and his team performed a genetic profile on these adults and then using a mathematical analysis, arranged them into 4 groups ranging from those having the lowest genetic risk for obesity to the highest genetic risk for obesity.
“What was interesting is those people with the highest genetic risk for obesity seemed to benefit the most from regular exercise. In other words, people with the highest risk for obesity based on their genes who exercised regularly had a lower BMI, lower % body fat and smaller waist and hips compared to people with the same genetic risk who didn’t exercise. So, those of us who are unlucky and gain weight more easily because of our genes can do something about it. This study shows that exercise can reduce obesity.
“Another interesting observation that came out of this study is that jogging appeared to be particularly effective at preventing body fat accumulation. In each of the 4 genetic groups in this study, people who reported jogging had lower body fat compared to people who didn’t regularly exercise. The message here? The sun is shining, grab some trainers and start trading in fat for muscle!”
Dr Katarina Kos, Clinical Senior Lecturer, Diabetes and Obesity Research, University of Exeter, said:
“Genes play a contribution to our overall weight and it takes a number of them together to make a difference. The study looks at 97 genes previously found to influence the BMI of Europeans, combined and on average the same genes play less of a contribution to people in Taiwan (1.9% variation in BMI). Whilst they make a relatively small difference to our overall weight, these gene combinations are not analysed in clinical practice.
“The authors find that if considering self-reported activity, that most types of exercise seems to be effective in tackling weight when mathematically linking it to the combination of genes. They consider regular activity to be exercise of 30 minutes three times a week. They looked the at frequency and duration of the self-reported sessions, but one limitation of the study is that intensity of the exercise was not recorded.
“As expected, the most popular activity in this cohort is walking and jogging whilst much fewer people (around 200 people or less) take up sports such as tennis, basketball, weight training etc, there, due to the small sample sizes, no conclusions can be drawn on the benefit of these particular sports. Additionally, as most people in real life are likely to vary activity, the impact on weight of a combination of sports has not been looked at. Despite this, the study finds that all sports seem to be associateD with a better weight or fat distribution (although these associations are not all significant). The good news is that being active helps managing our weight and improves our fat distribution to reduce the risk of ill health.”
Dr Jennifer Logue, Clinical Reader and Honorary Consultant in Metabolic Medicine, Lancaster University, said:
“This was observational research with self-reported activity levels; controlled clinical trials would be needed to prove these finding and change clinical guidelines.
“Physical activity in general is important for maintaining a healthy weight. While this study suggests that high intensity exercise may be better for preventing obesity in those at higher risk, the key is to find an activity you enjoy and can sustain in the longer term.”
Dr Simon Cork, Lecturer in Medical Education, King’s College London (KCL), said:
“Two things stand out from this study that are worthy of mention. Firstly, the study was performed only on people of Han Chinese ethnicity. It is not clear whether the results from this study will be applicable to say Caucasian or Afro-Caribbean individuals, who may have different genetic predispositions.
“Secondly, while the effects on various measures of body weight were significant for the types of exercise highlighted, their actual effects on parameters such as body mass index, hip circumference and body fat percentage were only minor. Various studies have shown that exercise alone is not sufficient to lose significant body weight in the absence of more general lifestyle changes (such as diet).
“So, while this study does suggest that some types of exercise are better than others (at least in the Chinese Han population), people should be cautious about employing these techniques as their primary source of weight loss.”
* ‘Performing different kinds of physical exercise differentially attenuates the genetic effects on obesity measures: Evidence from 18,424 Taiwan Biobank participants’ by Lin et al. was published in PLOS Genetics at 19:00 UK time on Thursday 1 August.
Dr Simon Cork: No conflicts to declare.
Dr Jennifer Logue: “No relevant CoI.”
None other received.