Is Fasting the Key to Weight Loss?

Several years ago, I watched a BBC Horizon documentary, "Eat, Fast, Live Longer".

http://www.bbc.co.uk/iplayer/episode/b01lxyzc/horizon-20122013-3-eat-fast-and-live-longer

Michael Mosley was looking at diets which may increase longevity. Some of the diets didn't look too appetising. Perhaps eating them just makes one feel as if life is longer!

The focus of the programme was on calorie restriction and fasting. It has been demonstrated in the laboratory that decreasing calorie intake leads to longer life in some animals. This may appliy to humans too.

After looking at low calorie diets, Mosely tried fasting. He discussed intermittent fasting, suggesting that eating normally for 5 days with a 2 days fast each week would have similar, achievable benefits as a permanent, low calorie regime. Unfortunately, this has evolved into the 5:2 fad diet which was never intended (I hope), since the programme was not about weight loss, but longevity. This 5:2 diet has really taken off, with books, cookbooks and God knows what else, making a lot of money for those jumping on its bandwagon.

Anyway, the programmme prompted me to try a 3 day fast, just to see its effect. I'm not quite sure why, but a thin consomme soup of about 50 kcals was permitted each day, so I had this each evening.

On the first day, I cycled 35 miles and felt fine afterwards. On the second day, I cycled the same route. Curiously, I did not feel hungry at all, but the soup on this day tasted absolutely delicious. By noon on this second day, I was already planning my first breakfast meal and lunch on day four. On the third day, I knew that my liver glycogen Ievels would be depleted, so I did not go out cycling, which is a pity because I am sure I would have coped very well. At that time, I wasn't fully aware of the body's mechanism for surviving in an absence of carbohydrates in the diet.

Although I still wasn't hungry, I was thinking of food constantly. By now, I had a mental plan of the following week's menus and the evening mug of soup, which I ate slowly with a spoon, was the most delicious I had ever tasted! Finally, after 78 hours, I broke my fast on a Saturday morning, eating a normal breakfast and a lunch about 5 hours later. I can't say I lost any body weight in such a short time (I wasn't looking for that), but clearly, a number of internal changes would have occurred.

When a human starves (and a fast is simply voluntary starvation) the body goes into survival mode. Firstly, we are constantly bombarded with thoughts of food, a I was. Food becomes an obsession. In Kurt Vonnegut's collection of short stories about war,  "Armaggedon in Retrospect", he describes his fellow prisoners-of-war, discussing and fantasising about food, planning future meals constantly. This is the experience of most people in similar situations. The brain is constantly reminding us, "Eat!! Eat! Eat!"

When it is obvious that there is no food available (or very little), the liver starts giving up its glycogen reserves and fat burning mechanisms are switched on, to burn the body's fat. This would have been happening to me by the third day. The liver converts fatty acids to ketones, which can be utilised by the muscles and brain instead of glucose. Both acetoacetic acid and beta-hydroxybutyric acid are used in the heart and brain. Acetone is a by-product of acetoacetic acid's degradation. These ketone molecules are used for energy in the body's cells  The vital organs and muscles run on these very successsfully. 

There is also a requirement for protein to maintain and repair vital organs. Skeletal muscle is relatively expendable, so the muscles are gradually consumed. Muscle protein, like meat in our normal diet, can be converted to glycogen via gluconeogenesis, if necessary, so people who criticise low carb diets, saying that the brain requires carbohydrate to function, are missing the point. The body can manufacture its own carbohydrate, if required, by gluconeogenesis.

So, if there is sufficient water available, the body organism can survive in this state, feeding itself on fat and muscle, very efficiently for several weeks. But there are two serious drawbacks to this fasting; firstly, the body is wasting away. Mental processes and sexual libido will fail and extreme lethargy will result, as the body's metabolism slows down in an effort to conserve energy.The other drawback is slightly more serious - death will soon occur, as the body is unable to sustain vital functions. However, if food becomes available soon enough, the effects of starvation can be reversed and recovery to normal weight and health can occur.

We can learn some important things about weight loss diets from the experience of starvation. Clearly, the body can survive very well for a short time on its own resources - protein and fat, without carbohydrate. This mechanim to survive when food was not ever-present, originates in the very beginning of human development. Humanity has survived food shortages for millions of years. We know this because we are still here!

If then, we could find an eating plan today, which mimics our prehistoric, starvation survival mode, it would be the ideal reducing diet. It would leave us satisfied after eating, providing enough protein to prevent muscle and organ deterioration, while encouraging the body to use up its own excess fat. Well, the good news is, such a diet exists already. It is variously known as LCHF, Banting or Atkins diet. It is probably the most successful weight loss system in history, based as it is on protein and high fat (prehistoric survival food), with very low amounts of carbohydrate.

As early as 1862, the idea of eating just fat and meat, with some leafy green vegetables was promoted in a leaflet by William Banting, a retired English undertaker, who  had been struggling with obesity all his life. You can read about him here;

http://en.wikipedia.org/wiki/William_Banting

A century later, in U.S.A., Dr Robert Atkins came to similar conclusions and made millions of dollars selling books explaining his plan, much to the chagrin of his envious peers. 

Since then, there has been much research on Low Carb, High Fat diets. Not only are they effective in weight loss, but they are also now being proven to be healthy, despite their high percentage of fats. Notice, an LCHF diet is not a high protein diet. It always irritates me when dieticians don't listen before quickly defending the orthodox diet, consisting of 50% carbs and rush off into unnecessary warnings about the perils of "too much protein". 

An LCHF diet provides most of its energy in fats (65-80%) with about 20% from protein. As we have seen above, in the absence of food, humans can live perfectly well without carbohydrates, which are a non-essentail macro-nutrient. However, the LCHF diet allows for about 5-15% of total calories from carbohydrate. This is made up mostly of green vegetables, berries, a few nuts and some cheeses.

In its initial stage, to stimulate weight loss, there is a very low carbohydrates intake - about 20g per day - to start nutritional ketosis (ketone burning). This continues for a few weeks, then as excess fat is steadily lost, a very gradual increase in carbohydrates to a moderate level can be sustained, without stopping fat burning. Ketone sticks can be used to detect ketones in the urine, to ensure that ketosis is continuing. 

Unless you become an athlete or a very physically active worker, you will continue to have a very moderate carbohydrate level thereafter, eating mostly home-cooked, natural foods.
If you would like to learn more about LCHF diets, look here;

www.dietdoctor.com/lchf

Update:
Previously, I recommended the Atkins website, until I saw promotion of their own-brand, processed crap in the guise of "healthy, low-carb food". Some folks just cannot resist making profit from the weaknesses and gullibility of others. Look here to see what I mean:

www.dietdoctor.com/atkins-greed-and-the-fairy-tale-cookies

This site below, has some good info;

www.authoritynutrition.com/low-carb-diet-meal-plan-and-menu/

My personal favourite is Diet Doctor, which is actually a translated Swedish website run by Dr. Andreas Eenfeldt.

NOTE for DIABETICS
Reducing dietary carbohydrates has an effect on blood sugar levels and insulin requirements. Therefore, it is essential that you monitor and modify your insulin medication carefully in consultation with your Doctor.