Mechanisms of Intermittent Fasting Unveiled

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Intermittent fasting (IF) is proven to have beneficial effects on aging, cancer, cardiovascular diseases and neurodegenerative diseases. However, it isn’t known whether the benefits of IF are due to caloric restriction (CR), as with fasting, or whether they’re due to changes in eating pattern. Recent studies have discovered that the browning of white fat can improve insulin sensitivity and energy expenditure by producing heat. Both exercise and cold exposure have been shown to transform white fat into brown fat.

A recent study by Kim et al. from the University of Toronto looked into the mechanisms underlying intermittent fasting’s effects on health. They separated mice into 2 groups: an IF group and a control group. The IF group was not fed for 1 day and then fed for 2 days in a row whereas the control group was fed daily. This went on for 4 months. By the end of the study, both groups had been fed the same amount of calories. After 4 months, the IF mice weighed significantly less and had increased insulin sensitivity and a more stable glucose metabolism. Additionally, they had a lower proportion of white fat because it had been converted into brown fat. The IF mice had higher levels of adipose vascular endothelial growth factor (VEGF). VEGF helps form new blood vessels and activates adipose macrophages (white blood cells) which are critical for the browning of white fat and heat production. Interestingly, IF led to the browning of visceral white fat while cold exposure leads to the browning of subcutaneous white fat.

The authors note that health is not solely about “what and how much” we eat but also “when and how often”.

 

Dietary Fibre Reduces Risk of Knee Osteoarthritis

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This month a fascinating report was published in Annals of the Rheumatic Diseases. It was a collaborative study between Tufts University (Boston) and the University of Manchester. Dai et al looked into the link between dietary fibre and knee osteoarthritis (OA). They used data from the Osteoarthritis Initiative (4796 participants) and the Framingham Offspring Osteoarthritis Study (1268 participants). The first group was followed for 4 years and the second group was reassessed after 9 years. The findings consistently showed that higher total fibre intake was related to a lower risk of symptoms of knee osteoarthritis (pain, stiffness, and swelling). It was unclear whether fibre had an effect on the result of knee x-rays.

The authors note that “there is increasing evidence suggesting that OA shares similar metabolic characteristics including obesity, dyslipidaemia and inflammation with cardiovascular diseases and diabetes”. Clinical trials have already shown the beneficial effect of dietary fibre on reducing body weight, blood pressure, blood sugar and in reducing circulating C reactive protein (a marker of inflammation). Increasing our intake of fibre can help improve musculoskeletal problems in addition to bettering our overall health. Fibre can be found in cereal grains, fruits, vegetables, nuts and legumes.

The Perfect Human Diet

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Last week I came across a documentary entitled “The Perfect Human Diet”. It was released last year and directed and produced by C J Hunt. Hunt had serious health problems from an early age and experimented extensively with diets. At the age of 46 he decided to travel the world in search of the perfect diet. His findings  support the Paleo diet. Those that are unfamiliar with it will find the documentary fascinating. Here is a summary.

We’re in the midst of an obesity and diet-related chronic disease epidemic. The US alone accounts for 300,000 to 400,000 deaths a year! There’s a lot of confusion related to diet, it’s complicated, the recommendations change and seem to be based more on beliefs than science.

The nutritional pioneer Weston Price studied native diets among tribal populations and found that they had better teeth and better facial bone structure than westerners. More recently, Kerin O’Dea from the University of Southern Australia conducted an experiment with a group of overweight Aboriginals living in cities. She sent them for seven weeks in the outback where they lived a hunter-gather lifestyle with a diet that was 50% to 60% animal based. They all lost weight and improved their health. Jay Wortman has studied Inuit populations and found that today a lot of them suffer from obesity, type II diabetes and metabolic syndrome. Traditionally they lived on low carbohydrate diets and so it’s hypothesised that the disease is linked to the modern high carbohydrate diets.

In 1863 a London undertaker named William Banting popularised a diet recommended to him by the famous physician Dr William Harvey. At the time Banting was 65 years old, overweight, had poor eyesight, poor hearing and joint pains. Two years later he had lost 50 pounds and regained his health. Dr Harvey had recommended that he stop eating bread, butter, sugar, potatoes and  stop drinking milk and beer. Instead he advised meat, fish, poultry, dried fruit, vegetables and wine.

From 1865 to 1965 the standard hospital treatment for obesity was to decrease carbohydrate intake. In the 1950s  the idea that fat causes heart disease, by it’s effect on cholesterol, began to spread. The fats were replaced by carbohydrates. They had suddenly become good! Today the US Diet Guidelines are to decrease portion size, decrease sugar, decrease salt, and decrease saturated fats.

Professor Loren Cordain is a leader in evolutionary diet and author of “The Paleo Diet”. In order to understand the Paleo Diet we need to go back in time…2 million years back in time! About 2 million years ago Homo Erectus appeared on the savannah of Africa. They were anatomically similar to us and evidence of hunting tools suggests that they consumed a lot of meat. This is backed up by recent analysis of Homo Erectus bone fragments. Their diet contained a huge diversity of food which differed from their predecessors’ diet which was mainly plant-based. The increased amounts of omega 3 fatty acids are thought to have been a precursor for brain growth and behavioural sophistication. Then, 230,000 years ago, Neanderthals appeared in Europe and 192,000 years ago modern humans appeared in Africa. They left Africa 75,000 years ago and entered Europe 45,000 years ago. Bone analysis suggests that the diet of Neanderthals and the first modern human was very similar to that of Homo Erectus.

Everything changed 10,000 years ago. Man decided to settle and use agriculture. Diets changed. Dairy and grains, like wheat, were included and the variety of food decreased. The period before 10,000 years ago is known as the Paleolithic era and the period after is known as the Neolithic era. In the 18th and 19th centuries the industrial revolution led to the refinement of sugars, grains and other foods. More recently processed foods have flooded the market and can constitute up to 70% of modern human diets.

The Paleo Diet theory is based on the fact that the Paleolithic era is much, much longer than the Neolithic era and it’s during the Paleolithic that modern humans evolved. Therefore, we have evolved to eat the diets of our Paleolithic ancestors which is why we struggle and have become unhealthy on modern diets. Voila!

Interesting though the documentary was, it didn’t give a full list of foods to eat and avoid, so I had a look on Wikipedia. The Paleo diets advocates: fish, meat (grass-fed), vegetables, fruit, fungi, roots and nuts. It suggests to avoid: grains, legumes, dairy, potatoes, refined salt, refined sugar and processed oils (Wikipedia).

Although the arguments in favour of the Paleo diet are compelling, I’m not entirely convinced. If obesity and ill-health are the result of the change in diet 10,000 years ago, how come obesity has only become more prevalent in the last 150 years (see “The Obesity Paradox“)? Are grains and dairy really that bad for us? In my opinion there are 2 influential factors that have driven the obesity and diet-related illness epidemic. Our physical activity has gradually decreased since the industrial revolution. Mechanisation and lately the widespread use of computers has meant that most of us spend our working days sitting and a lot of us spend our leisure time sitting as well. During the same period our diets have changed drastically and now include a lot more refined and processed foods. These convenience foods as they are also known are high in sugars, salts and saturated fats.

I agree that variety is key to a balanced diet and the Paleo diet does put forth a solid case for eating meat…or against vegetarianism and veganism. That said, we should bear in mind that the meat our Paleolithic ancestors ate is very different to the meat we eat today. Theirs came from wild, lean animals whereas today’s commercial meat comes from sedentary fattened stock!

The search for the perfect human diet continues…

 

 

 

Exercise Encourages Healthy Eating

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Researchers have recently postulated that exercise may help encourage healthy eating! How? By changing the structure and function of the brain! The result of which is an enhanced inhibitory control. What this means in layman’s terms is that we no longer have to succumb to the temptation or lack of restraint that causes our over indulgence in food.

So, in addition to increasing our metabolism and burning more calories, exercise also improves our diet. What are you waiting for?