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We all know that most people who are overweight have eaten too much, or eaten the wrong types of food, or a combination of both. But what about those people who have genuinely stuck to the dieting rules but the weight insists on sticking to them? Experts have put forward varying explanations over the years. Current theories include genetics and chronobiology.
Nutrigenomics and Nutrigenetics
It is accepted that some people are genetically susceptible to weight gain, though no-one is genetically doomed to obesity, they just need to follow a genetically appropriate diet and exercise regime. Nutrigenomics is the identification of genes that are involved in physiological responses to diet and the genes in which small changes, called polymorphisms, may have significant nutritional consequences. Nutrigenetics is concerned with the effects of our individual genetic variations in response to diet and other sources of nutrients. It is the study by which dietary components communicate with the genetic material and how genetic variations affect interactions between these bioactive dietary components and the health and disease potential of a person.
Our ancestors were programmed to deal with harsh times, with little to eat during the winter months. Typically people would lose weight by the end of winter and they would eat more during the times of plenty – the summer months. Whatever the season, they would be unlikely to eat during the hours of darkness. Now we eat well throughout the year. This would constitute a polymorphism, as would extending the hours during which food is eaten.
Chronobiology
Chronobiology has been referred to as the biology of time, or the scientific study of internal biological clocks. It indicates the effect of time on living systems and of biological rhythms.
The human body has many ‘clocks’, such as the time to puberty, to menopause, and ageing clocks. According to researchers at the Salk Institute for Biological Studies (UCSD), every organ has a clock. This means there are times of day when the stomach, intestines, liver, heart etc will work at peak efficiency and at other times they are more or less sleeping. This is a concept that has been understood for millennia by traditional forms of medicine such as TCM, e.g. the optimal time for stomach efficiency is 7am – 9am, though chronobiology isn’t necessarily linked with these meridian energy clocks.
Having precise times of therapeutic opportunity to achieve optimal results for the body’s various organs and systems means that an ‘out-of-sync’ body clock can adversely impact the health of individual organs, sleep patterns, biological systems, metabolic efficiency and, it is believed, weight management. The daily or circadian clock relates to biological oscillations in activities that recur within a period of about 24 hours, including controlling such activities as eating. Metabolic cycles are critical for processes from cholesterol breakdown to glucose production, and they should be primed to turn on when we eat and back off when we don’t, or vice versa. But when people eat frequently throughout the day and night, it can throw off those normal metabolic cycles.
According to research carried out in 1989 by Prof Franz Halberg, certain aspects of eating behaviour, such as the time of day meals are eaten, may have important consequences for weight control. More recent research is confirming the theory that for some people when you eat could be just as important as what you eat, and possibly even more so. Experimental studies have found that restricting feeding times can have a profound effect on several metabolic functions including cortisol secretion, gastrointestinal motility and the activity of digestive enzymes.
In relation to weight management, how does the concept of chronobiology work in practice? Researchers from the Salk Institute fed mice a high-fat, high-calorie diet but altered when they were able to eat. One group had access to food both day and night, while the other group had access to food for only eight hours at night (the most active period for mice). In human terms, this would mean restricting eating to an 8 hour period during the day. Despite consuming the same number of calories, mice that had access to food for only eight hours stayed lean and did not develop health problems like high blood sugar or chronic inflammation. The all-day access group, on the other hand, became obese and were plagued with health problems.
We know that genetically we haven’t been programmed to eat at all hours of the day and night and this suggests the human body may benefit from the break it receives while fasting, whereas constant eating may lead to metabolic exhaustion and health consequences like weight gain. Researchers said their latest work shows it’s possible to stave off metabolic disease by simply restricting when you eat, with periodic fasting, or even by just keeping to regular meal schedules rather than “grazing” off and on all day. Grazing has been one of the mainstays of nutritional therapy recommendations in recent years. Whilst the research doesn’t mean that grazing isn’t right for some people, and it is likely to be appropriate where some health problems are concerned, there is logic to an extended period between meals for many people.
High carbohydrate intake
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These days the Western diet tends to be high in carbohydrates that the body converts into the glucose we need to create energy to sustain us throughout the day. But glucose in excess of requirements needed to sustain metabolic functions and provide immediate energy needs will be stored as glycogen in the liver and muscles, and when those stores are full glucose is converted into fats and stored in adipose tissues. Adipose tissue, currently considered as an endocrine organ, has the circadian clock machinery, influencing its hormones such as leptin and adiponectin.
The human body has another pathway for energy production, beta oxidation, whereby stores of fat are released from adipose tissues and converted into energy when glucose and glycogen stores are exhausted. It is considered it takes about six to eight hours for the body to metabolise its glycogen stores and after that it starts a shift to burning fat. Many people are eating carbohydrates regularly throughout the day and evening, so effectively they are having a continual flow of glucose into their bloodstream and may never leave a sufficient length of time for the body to need to switch to its beta oxidation pathway. Hence, they make it difficult for themselves to lose weight.
Intermittent fasting
Restricting the period of time in which food is eaten to about seven to eight hours daily follows the pattern of our ancestors, who rarely had access to food 24/7 and their only light was from the sun. Our genes are optimised for this eating pattern, which has been called intermittent fasting. Research suggests that sudden and intermittent calorie restriction appears to provide the same health and weight benefits as lengthy periods of continual calorie restriction. This may be helpful for those who can’t successfully reduce their everyday calorie intake. Fasting doesn’t mean abstaining from food for extended periods of time; this can be dangerous and counterproductive. Rather, intermittent fasting is a dramatic reduction of calorie intake – whether you opt for a 16- or 20-hour fast once or twice a week, or fasting every other day. Or a simple start might be to delay certain meals, such as having your first meal of the day later than normal, or exercising on an empty stomach, or ending meals earlier in the evening and fasting for a longer period overnight.
It’s vitally important to maintain an intake of 1.5 – 2 litres daily of hydrating fluid during any period of fasting. Fasting isn’t appropriate for everyone. Pregnant or breastfeeding women, diabetics, or those with hypoglycaemia may be best served to avoid it entirely until blood glucose and insulin levels are normalised or the baby is weaned. The involvement of the GP would be appropriate for these and other vulnerable groups of people but for a healthy person, intermittent fasting may help give a boost to health, especially if the person has already mastered an appropriate nutritious diet, which really should be the first step.
Exercising on an empty stomach has been shown to have a number of health and fitness benefits. Part of the explanation is that this regimen complements the sympathetic nervous system (SNS) along with the capacity to burn fat. The body’s fat burning processes are controlled by the SNS, which is activated by exercise and by lack of food. The combination of fasting and exercising maximizes the impact of cellular factors and catalysts, which encourages the breakdown of fat and glycogen for energy.
In regard to chronobiology, here are three studies from recent years investigating fasting for weight loss, all of which demonstrate the theory that when you eat could be as important as what you eat:
- Non-obese patients lost an average of four percent of their total fat with alternate-day fasting for 22 days. Their fasting insulin also decreased.
- Alternate-day fasting was effective for obese patients in a 2009 study. On fasting days participants consumed 25 percent of their daily calorie needs. On average, they lost just over 5.5 pounds in eight weeks, and about three percent of their total body fat.
- In young, overweight women, alternate-day fasting was just as effective as calorie restriction for promoting weight loss.