SLEEP & OBESITY

Sleep that is of good quality, adequate duration, and aligned with the body clock is vital for human health. In contrast, poor sleep and body clock disturbances contribute to an increased risk of adverse health conditions, including cancers, dementia, and cardio-metabolic diseases—a group of interrelated conditions such as diabetes and high blood pressure. Sleep disturbances and cardio-metabolic diseases are also strongly linked to obesity, a condition characterised by elevated body weight due to excessive accumulation of fatty tissue.

Not getting enough sleep and obesity

It is believed that people are sleeping less than before. Sleep duration has declined in recent decades worldwide, partly due to changing work schedules and the increase in sedentary jobs that involve little to no physical activity.

Research shows that self-reported short sleep duration (less than seven hours daily) is associated with a higher risk of obesity. Shortened sleep disrupts hormones that regulate food intake, namely ghrelin and leptin. Changes in sleep patterns can also affect areas of the brain responsible for reward processing, potentially leading to food-seeking as a reward behaviour. Additionally, shorter sleep duration and longer waking hours provide more opportunities to eat, including late-night snacking. However, the body metabolises food less effectively at night.

Sleep deprivation also increases fatigue, promoting a sedentary lifestyle and reducing motivation for exercise and healthy food choices.

Shift work and obesity

More than 15% of Australians engage in shift work, which increases the risk of obesity and type 2 diabetes. Cardiovascular risk factors such as abdominal obesity, high blood pressure, elevated blood sugar and fat levels, and low levels of "good" (HDL) cholesterol are more prevalent among shift workers.

Shift workers often experience fragmented and shortened daytime sleep and disruption to their body clock. Such changes to the sleep-wake cycle can increase energy intake, impair blood sugar regulation, and damage blood vessels. These effects are worsened when sleep restriction is combined with irregular meal timing, such as eating at night when the body is biologically programmed for sleep.

Interventions that alter meal timing or restrict the daily window for food consumption have shown promise in improving glucose metabolism and promoting weight loss. Time-restricted eating, which involves limiting food intake to a period of 8–10 hours during the day, may help prevent cardio-metabolic diseases in individuals exposed to circadian and sleep disruptions, such as shift workers.

Obstructive Sleep Apnoea (OSA) and obesity

Obstructive Sleep Apnoea (OSA) is a common disorder characterised by repeated episodes of obstructed breathing during sleep. This condition causes sleep fragmentation and often results in daytime sleepiness. OSA is an independent risk factor for cardiovascular disease and is linked to type 2 diabetes, high blood pressure, and abnormal cholesterol levels.

Continuous Positive Airway Pressure (CPAP) therapy has been the gold standard for OSA treatment for over 25 years. CPAP involves using pressurised air through a nasal mask to prevent airway obstruction during sleep. It is highly effective, reducing daytime sleepiness, improving sleep-related quality of life, and modestly lowering blood pressure.

Obesity is a primary risk factor for OSA, alongside age and male gender. Several factors link obesity to OSA:

• Excess fatty tissue in the upper airway walls and tongue narrows the airway, making it prone to collapse during sleep.

• Central obesity (fat around the stomach and abdomen) alters breathing patterns, reducing airway diameter and increasing the risk of airway collapse.

• Obesity may also affect the hormone leptin, altering respiratory control and promoting OSA.

Weight loss and OSA

Weight reduction may serve as a treatment option for OSA. Studies show that greater weight loss leads to significant improvements in OSA symptoms. Weight loss also enhances glucose and cholesterol metabolism and lowers blood pressure. However, individual responses to weight loss vary significantly, and further research is needed to identify those who benefit the most.

OSA may also contribute to obesity and related cardio-metabolic diseases. For example, OSA can promote weight gain by disrupting hormones that control hunger and metabolism and by reducing motivation to exercise. This combination reduces fat burning and increases food consumption.

There is evidence that OSA may slow down weight loss. Studies show that individuals with OSA participating in long-term weight loss programmes lose less weight than those without the condition.

Combining therapies for better outcomes

Weight management, combined with CPAP and other OSA therapies, is essential for reducing OSA severity. Tailored weight loss programmes that consider individual patient preferences are now recommended in practice guidelines as part of the treatment strategy for overweight or obese individuals with OSA.

Date: Feb 25; By: Sleep Health Foundation