Shift workers use of time-restricted eating and cardiometabolic health

14th October 2022

Shift workers use of a time-restricted feeding strategy may help to improve cardiometabolic health according to a recent randomised trial

Shift workers (SWs) including healthcare staff and front-line individuals such as police and fire-fighters are exposed to electric light, especially at night and which may disrupt sleep and biological processes controlled by endogenous circadian clocks, potentially resulting in adverse health outcomes. Moreover, in a population health study with 4155 SWs and 8258 non-shift workers, the former group were 17% more likely to be obese and 27% more likely to have diabetes, suggesting that this pattern of working, which disrupts the circadian rhythm, is associated with adverse cardiovascular outcomes.

Although SWs appear to be at a higher risk of adverse cardiometabolic outcomes, there is a lack of data on potential life-style modification interventions to improve their health. One study in which fire-fighters adopted the Mediterranean diet found that adherence to the diet was associated with markers of decreased cardiometabolic risk.

A lifestyle modification which is attracting research interest is time-restricted feeding (TRF) and epidemiological studies have indicated that maintaining a consistent long overnight fast, which is a form of time-restricted eating, can significantly reduce risks for chronic diseases.

Whether time-restricted eating could improve cardiometabolic markers among shift workers has not been examined and was the subject of the present, randomised trial by a team of US researchers. The researchers explored the feasibility of a 10-hour TRF pattern among fire-fighters who worked a 24-hour shift. Individuals were randomised to standard care, in which there was no restriction on feeding time or the TRF, which was set at 10-hours and maintained for 12 weeks.

Both the TRF and standard care groups were advised to follow a healthy Mediterranean diet and used a smartphone asp (myCircadianClock) to record food intake. Although all individuals were generally healthy, a proportion did have at least one cardiometabolic risk factor such as an elevated body mass index (BMI), hypertension, elevated LDL cholesterol and researchers also examined the impact of TRF among this subgroup.

Shift workers time-restricted feeding and cardiometabolic health

A total of 137 fire-fighters with a mean age of 40.36 years (91% male) were randomised to TRF (70) or standard care and among the whole cohort, 71% had at least one cardiometabolic risk factor.

In the group assigned to TRF, the mean feeding window reduced from a mean of 14.13 hours at baseline to 11.13 after 12 weeks (p < 0.001) whereas it was unchanged in the standard group.

Fasting glucose and insulin levels in both TRF and control groups were not significantly different after 12 weeks. In contrast among the TRF group, diastolic blood pressures were significantly reduced, as was weight and very low LDL cholesterol particle size.

When the researchers focused on the changes among the TRF group with elevated baseline risk factors, they observed significant reductions in fasting glucose, %HbA1c levels, systolic and diastolic blood pressure and C-reactive protein levels.

The authors concluded that TRF was a feasible intervention for 24-hour shift workers and may serve as a novel intervention to prevent cardiometabolic disease.

Citation
Manoogian ENC et al. Feasibility of time-restricted eating and impacts on cardiometabolic health in 24-h shift workers: The Healthy Heroes randomized control trial Cell Metab 2022

Time-restricted eating in type 2 diabetes improves glucose homeostasis

5th August 2022

Time-restricted eating for as little as three weeks in type 2 diabetes improves glucose homeostasis but does not affect insulin sensitivity

A time-restricted eating (TRE) pattern which limits intake of food to a 10-hour window can improve glucose homeostasis but not insulin sensitivity according to the results of a randomised, cross-over trial by Dutch researchers.

Any changes to the day–night rhythm due, for example, to shift work and subsequent changes in eating patterns is associated with body weight gain and impaired glucose tolerance. Moreover, some data also indicate that night shift work, especially rotating shift work, is associated with higher risk of type 2 diabetes.

Time-restricted eating could have health benefits and some evidence for this arose from a study which found that the daily duration of food intake exceeded 14.75 hour for half of the cohort. As part of this study, when researchers asked overweight individuals with a >14 hr eating duration, to restrict food intake to only 10-11 hours per day for 16 weeks, they reduced body weight and reported higher levels of energy and had improved sleep. 

Other work has revealed how TRE improves 24-hour glucose levels and among men with pre-diabetes, whereas the use of a 12-hour TRE pattern improved insulin sensitivity, β cell responsiveness, blood pressure, oxidative stress, and appetite. 

But whether a time-restricted eating regime could benefit those with type 2 diabetes remains unclear, although in one feasibility study, it was found that a TRE regime did not significantly improve measures of glycaemic control or reduce body mass.

Despite this, the effect of TRE on other metabolic health parameters is largely unknown and was the subject of the present study.

The Dutch team recruited adults with type 2 diabetes and a HbA1C of 6.4% and asked them to participate in a 10-hour TRE regime for 3 weeks in comparison to a control group whose food intake was spread over a period of > 14 hours/day and then the TRE group crossed-over after a 4 week wash-out period. Since the liver plays an important role in the regulation of blood glucose and that among those with type 2 diabetes, nocturnal glucose levels are elevated, the authors speculated that a TRE regime might reduce nocturnal glucose levels and therefore improve insulin sensitivity.

Time-restricted eating and glucose levels

A total of 14 adults with a mean age of 67.5 years (50% female) were recruited into the trial.

The mean 24-hour glucose levels were lower among the TRE group compared to controls (6.8 vs 7.6mmol/l, TRE vs control, p < 0.01). However, there were no significant differences with insulin sensitivity (19.6 vs 17.7 mcmol/kg/min, TRE vs control, p = 0.1).

There were also no changes in 24-hour energy and substrate metabolism between the two groups, although the time-restricted eating group did spend a significantly longer period of time with blood glucose levels within the normal range (15.1 vs 12.2 hours, TRE vs control p = 0.01).

The authors concluded that TRE provides an additional strategy to maintain 24 hour glucose homeostasis in free-living subjects with type 2 diabetes.

Citation
Andriessen C et al. Three weeks of time-restricted eating improves glucose homeostasis in adults with type 2 diabetes but does not improve insulin sensitivity: a randomised crossover trial Diabetologia 2022

Time-restricted eating reduces CVD risk in breast cancer survivors

9th June 2022

A feasibility study has found that a pattern of time-restricted eating in older breast cancer survivors reduces cardiovascular risk

Utilising time-restricted eating (TRE) in older breast cancer survivor patients with recognised cardiovascular risk factors, appears to reduce their overall risk, according to the findings of a feasibility study by researchers from the University of Toronto, Canada.

The World Health Organization has identified that globally in 2020 there were 2.3 million women diagnosed with breast cancer and which resulted in 685,000 deaths. Fortunately however, the overall 5-year breast cancer survival rate is 85% although this does depend upon the stage at which the cancer was detected and is less for those with later stage disease, for example, 1-year survival for those with stage 4 is only 66%.

Despite these high survival rates, it seems that breast survivors are at greater risk of cardiovascular-related mortality compared with those without cancer. In fact, a 2017 systematic review concluded that cardiovascular disease (CVD) is an important cause of death following breast cancer.

Consequently, strategies directed at reducing CVD risk among breast cancer survivors are likely to be highly beneficial. One such strategy which has attracted much attention in recent years is time-restricted eating (TRE), a form of intermittent fasting based on the circadian rhythm.

For example, one approach, 16:8, allows individuals to eat ad libitum but only during an 8-hour window, e.g., between 12 and 8 pm. TRE could help to reduce CVD risk and in a 2020 systematic review, the authors concluded that TRE is a promising therapeutic strategy for controlling weight and improving metabolic dysfunctions in those who are overweight or obese.

Given the elevated risk of CVD-related mortality among breast cancer survivors, the Canadian team wondered if TRE could reduce this risk, especially among those with pre-existing risk factors such as older age, being over-weight or obese and those who had completed a course of cardio-toxic chemotherapy such as anthracyclines, within 1 to 6 years.

The researchers enrolled a group of such women and asked them to eat as much as they wanted, but only between 12 and 8 pm and to only drink water, black tea/coffee outside of this feeding window, for a period of 8 weeks. During the study, participants were given access to behavioural support from a registered dietician.

The researchers calculated participants’ 10-year Framingham CVD risk and collected demographic and clinical data e.g., glucose and cholesterol levels as well as blood pressure, waist circumference, visceral adipose tissue (VAT) and whole body fat-free and fat mass.

Time-restricted eating and cardiovascular outcomes

A total of 22 participants with a mean age of 66 years and a mean body mass index (BMI) of 31 were included in the study. Fat-free mass did not change during the study period, although calorie intake was significantly reduced by a median of 450 kcal (p < 0.001).

At baseline, 68% of women were classed as cardio-metabolically unhealthy and this reduced to 53% at the end of the study.

The median Framingham CVD risk score reduced from 10.9% at baseline to 8.6% (p = 0.037), although modifiable factors in this score such as total cholesterol and systolic blood pressure were not significantly different. In addition, the mean BMI did not change whereas both VAT and whole body fat mass were significantly lower.

The authors calculated the TRE led to a 2% absolute reduction in CVD mortality risk and suggested that if this was maintained over time, TRE could reduce health costs and improve patient outcomes. They concluded by calling for randomised trials to further evaluate and confirm the value of this intervention.

Citation
Kirkham AA et al. Time-Restricted Eating to Reduce Cardiovascular Risk Among Older Breast Cancer Survivors J Am Coll Cardiol CardioOnc. 2022