Updated: Sep 25, 2020
More than two-thirds (>66%) of Australian's are overweight or obese, meaning these people are carrying an excess of body fat. Obesity is associated with an increased risk of pre-diabetes, type 2 diabetes, cardiovascular disease and at least 13 types of cancer.
Obstructive sleep apnoea, fatty liver disease, osteoarthritis, gallstones, PCOS, and overall disability are also associated with obesity. Excess body fat negatively affects every organ in your body.
Short-term fad diets do not fix obesity. Yes… they result in weight loss, however evidence shows 80-99% of people who manage to lose substantial weight will regain that weight within 1 to 3 years.
To approach sustainable weight loss and long-term weight management, a holistic approach that addresses a number of strategies must be incorporated into your lifestyle to achieve success. Obesity results from a complex mix of genetic, evolutionary, psychosocial and physiological factors.
Excess intake of processed foods, large meal portions, inadequate plant-based wholefoods and a sedentary existence are obvious drivers of obesity. However, your weight status is also dictated by your gut microbiota and its direct influence on your nervous, immune, digestive and endocrine systems. It is therefore essential to consider the affects of the following for sustainable weight loss and long-term weight management:
· Food quality and timing of meals (not just quantity of calories)
· Sleep quality and circadian rhythms
· Gut health
· Exercise type and amount
· Sunlight and vitamin D
· Stress levels
Results from impaired insulin signalling in muscle, liver and adipose tissue, resulting in reduced whole-body glucose uptake. In basic terms, this means it is difficult for blood glucose to move into your body cells. It is characterised by high blood glucose levels as well as hyperinsulinaemia; as your body tries to compensate by making more insulin to shuttle the glucose from your blood into your cells. Insulin resistance can and often leads to pre-diabetes, metabolic syndrome and eventually type 2 diabetes. Hyperinsulinaemia results in a pro-inflammatory and pro-growth state and is associated with obesity (central obesity), diabetes, cardiovascular disease and various cancers.
Insulin resistance is not caused by an excess consumption of carbohydrates. More so, it is caused by an excess consumption of saturated fats that result in intramyocellular fat deposition, dysbiosis and central adiposity.
Ultimately, a low-fat, high fibre, plant-based wholefoods diet has been shown to significantly reduce insulin resistance, despite containing moderate to high amounts of carbohydrates.
Sleep and Circadian Rhythm
Circadian rhythms are mental, physical and behavioural changes that follow a daily cycle. They respond primarily to light and darkness in your environment. Being awake during the day and sleeping at night is a light-related circadian rhythm.
Your biological clock is your innate timing devise. It’s composed of specific molecules that interact in cells throughout your body. Biological clocks are found in nearly every single one of your tissues and organs. They produce your circadian rhythms and regulate their timing.
Within your brain, you have a master clock that coordinates and keeps in sync all the biological clocks in the rest of your body. Your master clock comprises a group of about 20,000 neurons that together form a structure called the suprachiasmatic nucleus (SCN). Your SCN in located within your hypothalamus (part of your brain) and receives direct input from your eyes.
The main factor influencing your circadian rhythms is daylight. Light can turn genes that control the molecular structure of your biological clocks on and off. The amount of light and dark you are exposed to can speed up, slow down, or reset your biological clocks, as well as your circadian rhythms. This is significant, because your circadian rhythms influence your sleep-wake cycle, your endocrine system, your eating habits and digestion, as well as your body temperature. Plus many other bodily functions.
Irregular circadian rhythms have been linked to numerous health conditions, including obesity, diabetes, depression and sleep disorders.
There are several rhythmically occurring phenomena that control your circadian rhythms. They are known as zeitgebers. Light is the most notable. During the daytime, light (particularly blue wavelength light) stimulates your optic nerves (in your eyes) to produce a hormone called melanopsin. Melanopsin inhibits the release of melatonin, in turn keeping you in a wake-state. In contrast, at night in the absence of light, your SCN stimulates melatonin production, which in turn makes you sleepy.
In the morning, larger amounts of cortisol and insulin are released. Interestingly, circadian rhythms control your insulin section and insulin sensitivity. Unless certain foods (e.g. carbohydrates) are consumed over the day, insulin production shortly diminishes in the morning and remains low over the day. You are most sensitive to insulin in the morning, and as the day progresses, you become more resistant to insulin. During sleep you are most insulin resistant.
Leptin, is a hormone released from your fat cells that informs your brain that you are not hungry and you have enough energy stored in your fat cells. Ghrelin on the other hand, stimulates appetite, increases food intake and promotes fat storage. Both of these hormones seem to follow a circadian pattern. And as previously mentioned, melatonin influences this function. With the advent of electricity, and the ever increasing use of screens and excess light at night time, circadian rhythms are becoming more and more affected. In modern society, people are less exposed to darkness at night as they are watching more TV and using their phones, ipads and computers late into the night. This in turn is inhibiting the natural release of melatonin and ultimately impacting individuals circadian rhythms and negatively impacting their overall health, including the above mentioned hormones.
Night shift workers have significantly high rates of obesity due to their excess exposure of unnatural light at night and disordered sleep and eating rhythms.
Food is also a circadian disruptor. High fat foods, frequent snacking and late-night eating have been shown to alter your sleep-wake cycle. All of these poor food habits can lead to altered melatonin production, and in turn, sleep disturbances and insulin resistance.
Notably, intermittent fasting, when performed appropriately, has been shown to reset a dysregulated circadian clock.