What Is The Intermittent Fasting Diet?
Intermittent energy restriction diets such as the 5:2 diet and other intermittent fasting models, are gaining popularity as options to support weight loss, but what is the intermittent fasting diet and are these the best methods for our patients?
The 5:2 diet, involves five days of ad lib eating and two non-consecutive days of 600 calories, per week. A clinical trial in obese men found that the 5:2 diet was as effective as, but not superior to, a standard energy-restricted diet at inducing clinically significant weight loss, but hunger was experienced more frequently by those in the 5:2 arm.
Intermittent fasting, another common form of intermittent energy restriction, is an eating pattern involving periods of fasting cycled with ad lib eating. Fasting periods are 16-hour fasts daily, which involves skipping either breakfast or dinner, and restricting eating to an 8-hour period, such as 1 to 9 pm, or 7am to 3pm.
In a systematic review of 12 clinical trials directly comparing intermittent fasting to continuous energy restriction, intermittent fasting appeared to have similar effects on reducing body weight and fat mass, and improving glucose homeostasis, compared to continuous energy restriction.
The current body of evidence suggests that fasting strategies are effective in losing weight and improving metabolic health; however, they are not superior to other methods of caloric restriction. If our patients can follow a fasting protocol with good compliance then we may encourage them to utilise this tool. However, if fasting is unachievable in a patient then there are many other weight loss programs that we have to offer.
BUT THERE IS MORE….
Is it best to fast in morning or evening?
Eating at regular intervals helps reset and train the circadian clock (body clock), whilst random eating patterns disrupts the circadian rhythm and affects metabolism.
For example, a study tracking the eating patterns of healthy, non-shift-working adult subjects, found many eat within a 15-hour time frame, with most subjects eating frequently and erratically throughout their waking hours, whilst fasting overnight. The subjects in the time-restricted feeding group reduced their body weight and noted improvements in energy and sleep. This indicates that the timing of daily calories, not just the amount of calories consumed can impact weight loss, and other aspects of health.
An intermittent fasting diet commonly recommends fasting overnight and through the morning, with food often being consumed in the afternoons and evenings. While this has been shown to have benefit for weight loss, it may not be the best option for patients with cardiometabolic disease. In fact, research indicates that early time-restricted feeding, a form of intermittent fasting that recommends consuming food early in the day, may be the best approach for these patients; as consuming meals later in the day, and into the night can disrupt circadian rhythms, and may have adverse effects on weight. This was demonstrated in a clinical trial whereby employing early time-restricted feeding led to an improvement in insulin sensitivity, blood pressure and beta cell function; and reduced patients’ desire to eat in the evenings, compared to a diet with no time restriction.
Scientists have begun unravelling how Early Time-Restricted Feeding benefits humans. It is now known that there is a ‘circadian transcriptome’, where the expression or activity of almost every gene in our genome possess circadian modulation. Many organs, such as the liver, contain nutrient sensing pathways, and operate under a circadian fashion and helps co-ordinate feeding and fasting diurnal cycles. Additionally, the night-time secretion of melatonin acts on the melatonin receptors on peripheral tissue, most notably the pancreas. Stimulation of the melatonin receptors on the pancreas suppresses insulin release, suggesting that evening consumption of carbohydrates may not be optimal for metabolic health.
Essentially, the body is better equipped at adjusting metabolism during daylight than the evening, highlighting that eating primarily during daylight hours is better for metabolic health.
Your practitioner will take your individual case into consideration when making dietary recommendations for you. There is a lot of information out there, we are here to help assess what is most applicable to you.