Nutritional therapy for diabetes mellitus is widely accepted as safe and affordable when compared to pharmacotherapy. However, the efficacy of the present state of nutritional therapy based on current recommendations is poor. It is estimated that nutritional therapy is able to reduce HbA1c levels by 1 to 2 percent under ideal circumstances. A weight loss of \>5% is needed to have any significant beneficial effects on the levels of HbA1c, lipids, and blood pressure. This would require extensive modification of lifestyle, including calorie restriction, regular exercise, and close supervision by health care professionals. For the majority of patients, adherence to such a regime on a long-term basis is not achievable or practical.Considerable effort is required to educate and reinforce the complex behavioural changes needed. A simpler dietary regime that would produce the necessary weight loss and good metabolic outcome is needed.
Rationale for use of Intermittent Fasting as Nutritional Therapy: Practicability, Efficacy and Safety.
Intermittent fasting (IF) has been practiced by humans since ancient times, out of necessity and for religious purposes. Numerous regimens of intermittent fasting exist:
1. Alternate-day fasting, with either a total fast or restriction of energy 60-70% below estimated requirements on alternate days.
2. Modified Fasting Regimens (such as the 5:2 diet which involves severe energy restriction for 2 non-consecutive days in a week and ad libitum eating for the other 5 days), a variant of alternate-day fasting.
3. Time-restricted Feeding where intake is restricted to a pre-defined time window daily, and fasting occurs for 12-21 hours of the day.
There is experimental and evolutionary evidence across microbes and animals that such fasting improves cardiometabolic health and survival. In mice, the preservation of beta cell function occurs through the mechanism of autophagy during fasting, and survival is prolonged in bacteria, yeasts, worms and mice when fasting that has been attributed to an alternative ketone-body like energy source during periods of caloric deprivation. The mechanisms of action proposed are that fasting triggers adaptive cellular stress responses, resulting in an enhanced ability to cope with more severe stress and counteract disease processes. In addition, by protecting cells from DNA damage, suppressing cell growth and enhancing apoptosis of damaged cells, fasting could retard and/or prevent the formation and growth of cancers.
In humans, there is increasing evidence that intermittent fasting produces improvements in various metabolic parameters that are potentially beneficial to Type 2 Diabetics, such as improvements in glycaemic control, lipid profiles and weight loss. For example, Carter reported equivalent reductions in HbA1c in individuals with Type 2 diabetes with 12 weeks of Intermittent Energy Restriction (IER) or Continuous Energy Restriction (CER) which had been achieved with greater reductions in insulin medications within the IER group. Arnason demonstrated improved glycaemic control and weight in 10 community-dwelling middle-aged Type 2 Diabetic adults over a six week period in which subjects underwent Time-restricted feeding intervention for 2 weeks.
Other than glycaemic control, intermittent fasting also benefits other cardiometabolic parameters. Body fat, LDL-Cholesterol, Triglycerides and weight circumference were reduced with improvements in glucose metabolism in obese subjects in response to an alternate day modified fast. Glucose metabolism, reflected by decrease in fasting insulin, improved in non-obese subjects when subjected to 3 weeks of alternate day fasting.
Alternate day fasting has been associated with hunger, distraction with lower perceived work performance and lower mood reported across some of its' human studies.Modified Fasting Regimens, though they largely result in clinically and statistically significant weight loss of between 3.2-8.0% have up to 15% of participants reporting negative side effects, such as feeling cold, irritable, low energy levels or hunger.
Time-restricted Feeding (TRF), typically have daily fasting intervals of 12-21 hours per day. There were no mean changes in tension, depression, anger, vigor, fatigue or confusion when subjects of a crossover trial were consuming one meal a day as opposed to an isocaloric diet consumed as three meals a day. There is observational evidence from Ramadan studies of Diabetic patients that glycaemic control and lipid parameters improve over a 4-week fasting period. Only one cross-over controlled study in healthy middle-aged adults has reported on metabolic outcomes with Time-restricted Feeding. Stote et al. found both pro-atherogenic changes (increased LDL cholesterol) and anti- atherogenic changes (increased HDL cholesterol and decreased TG) following 8 weeks of limiting food intake to one evening meal. This might have been confounded by circadian variations of baseline and post-intervention blood measurements, that were taken in the morning and evening respectively. Thus far, there are no publications on interventional studies on Time-restricted Feeding in diabetics to the investigators' knowledge. Time-restricted Feeding appears to be the most practical and easy to learn regime among all the intermittent fasting variations.
The investigators decided to adopt TRF and make it into a standardized regime that requires the subject to aim for a continuous fasting duration of 16 hours per day. The instruction can be taught to patients in a 30 minute session and opportunistic reinforcements. This mimics a real world counselling encounter between a primary care physician and patient with diabetes mellitus. The investigators call this regime Time Restricted Eating As Treatment (TREAT). This 12-week study of TREAT in adult patients with Type 2 Diabetes Mellitus aims to explore if this simplified form of intermittent fasting can result in clinically and statistically significant reductions in weight, improved glycaemic control and metabolic parameters including hyperinsulinemia, with particular emphasis on an Asian population. Accordingly, the investigators plan to recruit 50 community dwelling type 2 diabetic patients and instruct them on TREAT in a clinic setting. Patients will then be followed up with anthropometry and biochemical markers pertaining to diabetes during the study visits.
