How diet affects longevity

How diet affects longevity

The increasing affluence of modern cities has created an environment where weight gain becomes effortless and maintaining your body in good health becomes a common pursuit. Weight loss solutions sprout to meet the demands for losing weight and people are bombarded with endless diet remedies that promise get-thin-quickly solutions.

With each diet solution purporting to be the best and most effective, how does one choose from these diet choices? A recent November publication in the Circulation: Cardiovascular Quality and Outcomes journal provides some answers.

Popular diets - do they work?

Among the four popular diet plans that were studied in the publication, three of them were low-carbohydrate diets, including the Atkins diet, the South Beach diet and the Zone diet. Millions of books on these three diets have been sold.

The Atkins diet is based on a very low-carbohydrate intake, with no limitation on protein and fat intake.

The South Beach diet is a low-carbohydrate, high-protein diet. It encourages the intake of low glycaemic index (GI) carbohydrates, lean proteins and unsaturated fats.

The GI is a ranking system that examines how carbohydrates affect blood sugars on a scale of 0 to 100. Low GI foods are digested and absorbed more slowly, resulting in a slower and more gradual increase in blood sugar.

Zone is a low-carbohydrate diet with consumption of low GI carbohydrates, low-fat proteins and small amounts of good fat. The Weight Watchers programme is a combination of personalised point system to restrict food calories, planned weekly group physical activity sessions and behaviour modification.

Randomised control studies of participants in the Atkins diet, Weight Watchers programme, and Zone diet showed similar weight loss in the short term (less than six months).

Only the Weight Watchers programme showed consistent efficacy in weight reduction.

However, most of the weight loss achieved in the short term was regained subsequently such that by 12 months, the efficacy of these three diet plans were similar to controls. This weight regain was especially seen in the Atkins diet. There was no difference between those on the South Beach diet and usual care.

Even for the Weight Watchers programme which is the only diet that seems to be able to show a consistent efficacy for weight loss, the weight loss in the real world practice is very modest.

In an observational study on participants put on a 12-month Weight Watchers diet in the Weight Watchers National Health Service Referral Scheme in the United Kingdom, the median weight loss was 2.8 kilograms at 12 months.

At 24 months, the data for Atkins and Weight Watchers suggest that even the weight loss achieved at 12 months appears to be partially regained at 24 months.

What the authors of the study found was that real world objective data on weight loss diets was very sobering and at best, the weight loss was very modest and short-lived in most participants.

This was a stark contrast to the marketing claims of the dream transformation of dowdy, overweight women to glamorous, slim women with these get-thin-quickly wonder diets.

Despite these illusory, impossible marketing claims, many will choose to pay for these programmes rather than opt for the disciplined and objective methods of weight reduction that have been supported by objective scientific evidence. Do popular diets reduce heart disease?

While there is some data for improvement in blood triglycerides in some of these diets, there is presently no data to show that any of these diets are able to reduce the "bad" or low density lipoprotein cholesterol (LDL-C). There is also no data to show any benefit in the lowering of blood pressure for both the South Beach and Zone diets.

The data for Atkins and Weight Watchers for blood pressure suggests that there may be some beneficial effect in the short term but the data at 12 to 24 months has been inconsistent.

More importantly, results from two long-term, head-to-head randomised control studies of participants in the Atkins diet, Weight Watchers programme and Zone diet showed no significant differences in risk reduction for heart disease.

Lifestyle changes

Despite the very modest results in these diet programmes, there is evidence that lifestyle changes can make a difference.

In a small randomised control study, the Lifestyle Heart Study, published in the Journal of the American Medical Association in 1998 by Ornish, intensive lifestyle changes - where diets contained 10 per cent fat, with a whole foods vegetarian diet, aerobic exercise, stress management training, smoking cessation and group psychosocial support - was shown to result in a decrease in heart artery narrowing.

More regression of heart artery narrowing was seen at five years than after one year in the intensive lifestyle change group.

In comparison, in the control group, narrowing of the heart arteries progressed and the number of adverse heart disease events more than doubled during the five years.

In a larger study published in the American Journal of Cardiology in 2003, the same intensive lifestyle change was shown to result in reduction in heart risk factors including lowering of blood pressure, lowering of LDL-C, weight reduction, and improvement in quality of life.

This Ornish diet is based entirely on diverse, nutrient-rich plant foods. Other diets, such as the Mediterranean diet, which also comprises mostly of plant-sourced food, has also been shown to provide a similar benefit for the heart.

There is no single formula for everyone and a different diet prescribed in the Diabetes Prevention Program prevented the development of Type 2 diabetes mellitus in 58 per cent of high-risk adults as compared to controls. Most of these successful weight-reduction programmes include lifestyle changes that go beyond pure dietary control.

Living to 100

Lifestyle changes can go a long way in increasing life expectancy. Interestingly, based on the Danish Twin Study, for the average person, our genes contribute only about one quarter of how long we live.

The highest proportion of people who reach 100 years is found in different locations such as the mountainous Barbagia region of Sardinia, Ikaria island in Greece, Nicoya Peninsula in Costa Rica, Seventh Day Adventists around Loma Linda in California and Okinawa in Japan - but they share common lifestyle traits.

Common traits in the lifestyle of these centenarians include:

Moving naturally: their environment constantly encourages them to be active without the need to run marathons or go to the gym - most do gardening.

Purpose: waking up every day with a sense of purpose is worth up to seven years of extra life expectancy. Stress reduction: they all have routines to reduce stress.

The 80 per cent Rule: these centenarians stop eating when they are 80 per cent full. They generally eat their smallest meal in the late afternoon or early evening and then they don't eat any more for the rest of the day.

Plant-based diet: Beans are the foundation of most centenarian diets. Meat consumption comprises mainly of 100 gm of pork once weekly.

Wine: Most centenarians except Adventists drink one to two glasses of red wine daily.

Community belonging: Attending faith-based services weekly will add four to 14 years of life expectancy.

Family first: Centenarians put their families first by looking after their parents and grandparents nearby or in their home, are committed to a life partner (which can add up to three years of life expectancy) and spend time with their children.

Socially healthy network: Centenarians live in social networks that promote healthy behaviour.

Hence the formula for longevity is a concoction of a plant-based diet of modest quantity accompanied by wine, purposefulness in life, reduced stress, living actively, having a socially healthy lifestyle, loving your family, and community belonging.

These are the simple ingredients that will help most people live to their 90s and if you are blessed with the right genes, you will cross the 100 mark.

Dr Lim is the medical director at the Singapore Heart, Stroke & Cancer Centre. He is also editor-in-chief, Heart Asia, a journal of the British Medical Journal Publishing Group; he chairs the scientific advisory board of Asia-Pacific Heart Association and is an honorary professor and senior medical adviser at the Peking University Heart Centre.

This series is brought to you by Heart, Stroke and Cancer centre. It is produced on alternate Saturdays.

To read more of Dr Lim's previous health-related articles, please visit:

This article was first published on November 29, 2014.
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