There is no doubt that to lose weight you have to take in less calories than you burn off every day. But, this is not as simple as eating less food and doing more exercise. New evidence is now emerging that it is not just what you eat but also when you eat.
Firstly, let us consider “Calories in”. “Calories in” is everything that goes in your mouth apart from water consumed in an inert container. All “calories in” have the potential of contributing to weight gain although, to take the example of an apple, the number of specific calories in an apple is actually less than the amount needed to metabolise the combination of nutrients found in the apple itself. Therefore, consuming an apple gives you a negative calorie balance which is therefore a help in losing weight. When you consider macronutrients, 1 g of fat contributes 9 cal, 1 g of carbohydrates and protein each contribute 4 calories. But, a significant carbohydrate load leads to more insulin release which tends to lay down more fat than the equivalent amount of fat and protein.
Fluid also has to be entered into the equation. If you consume water in an inert container such as a glass or a stainless-steel bottle, then this is not contributing to your calorie intake. Many people these days, however, consume water in a plastic bottle which leeches a vast array of, at times, quite damaging chemicals into the water which can significantly affect metabolism and contribute to weight gain.
Most people, however, also consume other forms of fluid such as tea, coffee, alcohol, juices, milk and the ubiquitous soft drinks, whether sugar sweetened or artificial. Alcohol, for example, contributes 7 cal per gram and when you add in the sugar added to the alcoholic beverage, there is a significant caloric intake with each standard alcoholic drink consumed. For example, I saw a patient a few months ago who had significant abdominal obesity. His wife supported his comments that he did not eat much but he went on to tell me that he consumed a bottle of wine on a daily basis which in itself gives him close to 1000 cal per day before he puts anything else in his mouth.
To focus on soft drinks, the amount of sugar in the sugar sweetened beverages is anywhere between 8–12 teaspoons per can and recent work has demonstrated that the artificially sweetened drinks contribute to an equivalent amount of weight gain despite the fact that the artificial sweeteners allegedly carry no calories.
Then we must look at calories out or in other words the energy we burn on a daily basis. There are 3 components here which include exercise, movement and metabolism. Unfortunately, the system is more geared to sin than it is penance. If you go for a brisk half an hour walk, you burn 300 cal. If you have a small piece of chocolate cake you are taking in 300 cal.
Another big issue is that of prolonged sitting. It is now estimated that the average person living in modern society sits for 11 h/day and this is associated with a whole host of health issues from musculoskeletal problems, cardiovascular disease, high blood pressure and even cancer and, of course, the increasing weight gain we see across the board in our society. Last comes the thorny and often misunderstood concept of metabolism. Metabolism is basically the day-to-day functioning of each cell in our body contributing to existence. To maintain normal balance requires a very finely tuned system involving energy production by a component of the cell — the mitochondria, along with thousands of various proteins which have a variety of functions within the body. The complex process of metabolism consumes a significant amount of energy on a daily basis and in fact over a 24-hour period the average person burns around 1500–1600 cal daily before any exercise or movement.
But, the human being is not like a car. With the car, you put the fuel in and you can use the petrol when you need it. With our bodies, if you do not burn the fuel within a few hours of ingestion, it gets laid down as fat.
Now to discuss the best studied diet, the Mediterranean diet. It is far too simplistic to look at the food that is ingested. In fact, it is the Mediterranean lifestyle that contributes significantly to their good health. They have a large breakfast of fresh fruits and whole grains and burn off any extra carbs in the hot Mediterranean sun in the morning. They have their biggest meal at lunchtime which typically involves pasta and a couple of glasses of wine (typically red wine). The carbs and alcohol make them sleepy and they have an afternoon sleep typically lasting around one hour and then burn off any extra carbs in the hot Mediterranean sun in the afternoon. In the evening, they have a small meal and go to sleep.
In Western society, we have a small breakfast and small lunch and typically snack throughout the day and have a huge evening meal and sit down for a few hours and watch television and then go to sleep. As we are not burning off any of the fuel taken in from our evening meal, it gets laid down as fat. Another major issue is the increasing sleep problems experienced by many people in modern society. 30% of adults experience some form of insomnia along with the very common sleep apnoea. As the body works on a 24 hour cycle, our so-called circadian rhythms are significantly affected by poor sleep as are many of the normal hormonal secretions throughout the day and can certainly affect our metabolism in a deleterious fashion.
Over the past decade, there have been increasing comments about the timing of eating. It appears that one of the bad habits of the modern world is to delay eating until late in the evening which appears to have a profound effect on metabolism. Prolonged delayed eating can lead to weight gain, increasing insulin and cholesterol levels and negatively affect fat metabolism and the hormonal markers implicated in heart disease, diabetes and many other health issues.
Professor Namni Goel, a professor of psychology in the division of sleep and chronobiology at the University of Pennsylvania has performed a very elegant study on 9 healthy weight adults subjecting them to 2 different conditions over an 8 week period. The first involved daytime eating of 3 meals and 2 snacks between 8 AM to 7 PM with a two-week washout in between. This was followed by delayed eating including the same amount of meals and snacks and Identical calories but staggered to between 12 midday to 11 PM. Sleep was kept constant throughout the study.
A variety of measurements were performed including weight, the respiratory quotient which looks at indirect measurement of metabolism, along with a number of hormonal markers. The study clearly showed that delayed eating led to a gain in weight, metabolising fewer fats and more carbohydrates, increasing levels of insulin, glucose, cholesterol and triglycerides.
The well-known hormone, Ghrelin, stimulates appetite and this peaked earlier in daytime eating along with Leptin which induces the feeling of satisfaction when you eat, peaked later. Therefore, eating earlier keeps you satisfied for longer and prevents excessive eating in the evening.
Therefore, weight gain and weight loss is not a simple question of how much we eat and how much we move but clearly also involves the very complex concept of metabolism. This is not a fixed parameter for each individual but can significantly be affected by many factors including age, genetics, the amount of food consumed, the type of food and now, when we eat as well.
As the father of medicine, Hippocrates, has been often quoted as saying, “Let food be thy medicine and medicine be thy food’. Although this is a very important comment, it is clearly not that simple.