help to guide novel weight-loss strategies. A study published on April 2, 2013, showed that eating behaviours, particularly night-time eating, contributed to weight gain during sleep loss. Whole-room calorimetry measured daily energy expenditure in adults undergoing 5-day cycles of inadequate (5 h) or adequate (9 h) nightly sleep. Energy expenditure was about 5% higher with insufficient sleep, but increased food intake more than compensated for this energetic cost. In the sleeploss condition, participants ate a smaller breakfast but consumed 42% more calories as after-dinner snacks, leading to weight gain. The study investigators suggested that participants’ eating patterns during sleep loss resulted from a delayed circadian phase—ie, a later onset of melatonin secretion at night, assessed by hourly blood samples from an intravenous catheter—which might have led to a circadian drive for more food intake. Furthermore, the time between waking and melatonin offset was longer in the 5 h sleep condition; thus, participants awoke during an earlier circadian phase (while still in

biological night) and might have been less hungry for breakfast. Previous studies have suggested that disrupted signalling of satiety and hunger hormones leads to the overeating associated with insufficient sleep; however, in both the 5 h and 9 h conditions, excessive food intake was accompanied by appropriate increases in the satiety hormones leptin and peptide YY and decreases in ghrelin, which stimulates hunger. Future studies should examine how sleep deprivation leads to delays in circadian phase and how circadian timing of meals affects energy metabolism. For the millions of people whose working week necessitates a disrupted sleep schedule, a physiological drive for more food intake, the availability of high-calorie foods, and exhaustion leading to less physical activity overall could be a potent formula for weight gain. Whether for work, play, or travel, voluntary sleep curtailment has become endemic; however, restricted sleep seems to interfere with the crosstalk between complex physiological and circadian networks

Oscar Burriel/Science Photo Library

In Focus

that have evolved to couple our bodily functions with the Earth’s 24 h rotation. Many more issues deserve investigation, such as the differential effects on health of acute versus chronic sleep deprivation, and how light exposure mediates the effects of sleep loss. As more evidence emerges of the circadian orchestration of metabolism, perhaps the time has come for sleep to figure more prominently in treatment and public health guidelines.

For the study on sleep, food intake, and weight gain see Proc Natl Acad Sci USA 2013; published online April 2. DOI:10.1073/pnas.1216951110

Jill Jouret

Technology Diabetes management goes digital Do you have a smartphone? About 50% of people in the UK and USA own a smartphone, and the popularity of such devices is increasing rapidly in emerging nations. According to a study by a software analytics company, the average smartphone user checks their phone every 6·5 min. The question for medicine is, can this enthusiasm for technology be harnessed to improve health? Management of diabetes, needing as it does regular checks of blood glucose and diet management, is one area that could be enhanced by the use of smartphones. This opportunity has not gone unnoticed

by the makers of mobile applications (apps). We tested three apps relevant to diabetes, from those listed as most popular with users of the Diabetes UK website. Glucose Buddy (up to £3·99, iPhone), aimed at people with type 1 or type 2 diabetes, allows users to track their blood glucose measurements and record glycated haemoglobin, medicine, food, and activity. The app can plot a graph showing trends in blood glucose over the course of measurements entered and the results are colour-coded, with the average result for each day being purple, the highest red, and the Vol 1 September 2013

lowest blue. This graph makes it easy to monitor the average and range of blood glucose measurements over days and weeks. A key feature of Glucose Buddy is that the graphs can be downloaded, making them easy to share. The makers of the app hope that it will help to improve communication between patients and caregivers. The app can be set to send so-called push reminders, meaning a message will be displayed on screen when the user should take a blood glucose measurement, based on the timing of the previous day’s entries. A link to the Glucose Buddy online forum is also included,

For more on Glucose Buddy see For more on Insulin Pro see insulindosecalculator/index.html For more on Carbs&Cals see en-us


Michael Donne/Science Photo Library

In Focus

in which people with diabetes can ask and answer questions about life with the disorder; peer support has been identified as one of the most important features of digital diabetes management. One drawback of the Glucose Buddy app compared with the traditional method of recording blood glucose in a logbook, is that logbooks usually present days in rows, making it easy to see patterns at different times of the day—eg, high measurements every morning. By contrast, Glucose Buddy puts each measurement in its own row, and the graphs only show a continuous temporal trend, making these daily patterns much harder to spot. Insulin pro (£1·49, iPhone) is aimed at people with type 1 diabetes. It helps users to calculate how much insulin they need based on six different factors: target blood glucose, correction factor, correction


dose, exercise, carbohydrate factor, and meal dose. An important feature of this app is that it gives automatic warnings when a user inputs a blood glucose concentration that is too high or too low. For values that are too high, a warning noise sounds and the message “KETONES, check ketones if glucose remains high” is displayed on screen. When a user enters a value that is too low, the warning sounds and the message “HYPO” is displayed. If the user has noted that they are exercising at the time of the measurement, a further warning is displayed: “There is a danger to exercise with hypo”. While these features might be helpful, other elements of Insulin Pro might be confusing to some users. In the UK, the Dose Adjustment for Normal Eating course teaches patients to calculate how much insulin is needed for 10 g of carbohydrates, and then uses that as a ratio—ie, 1:1 is 10 g of carbohydrates needs 1 unit of insulin, 1:2 is 10 g of carbohydrates needs 2 units of insulin. By contrast, Insulin Pro asks how many grams of carbohydrate is equivalent to 1 unit of insulin, which can result in ratios that are more difficult to work with—eg, 1:1·25. Carbs&Cals (£3·99 iPhone, Android, and Blackberry) is a food and drink database providing nutritional information—calories, carbohydrates, protein, fat, and fibre—for more than 2000 items, together with photographs that can be used to guide

portion size. The user selects what they have eaten from the database and the app calculates the total nutritional content for each meal and saves this information to a calendar, so that it is easy to look back at eating patterns over weeks and months. The app encourages users to set a target for weight loss and then calculates a daily target for carbohydrates, calories, protein, and fat. The emphasis on diet makes this a useful app for those with type 2 diabetes, or for those with prediabetes, for whom weight loss is a priority. Diabetes apps have many useful features, but they also have flaws and need to be used alongside traditional management methods. As with all apps, there are potential issues around data privacy, and patients should be encouraged to check that their information is secure. Clinical studies of the effectiveness of diabetes apps can be expected, but with the increasing popularity of apps, especially among young people, caregivers will not be able to wait for these results before offering advice to patients. To help patients use these aids effectively and safely, caregivers will need to engage with their patients to find out which apps they are using. Apps have the potential to benefit diabetes management, but it is up to clinicians and patients to ensure these benefits are maximised.

Maria Danes, Frances Whinder Vol 1 September 2013

Diabetes management goes digital.

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