Perhaps it has something to do with New Year’s resolutions – three different lots of research into weight loss made headlines in the first quarter of 2013.
Each research project focused on a different aspect of eating.
What we eat: the role of sugar
The World Health Organisation commissioned New Zealand research that was published in the British Medical Journal (BMJ). A team from the University of Otago examined 7895 international trials and 9445 cohort studies before aggregating the findings of 68 studies that looked directly at the effects of sugar on body weight. The researchers found that reducing free sugars in the diet has a “small but significant” effect on body weight in adults – an average reduction of 0.8 kg. Increasing sugar intake was associated with a corresponding 0.75 kg increase in body weight, which is reported to occur comparatively rapidly. Study durations ranged from 10 weeks to 8 months. However, the researchers reported that the weight loss or gain would be cumulative (keep on going) for as long as a subject continued on an increased or decreased consumption of free sugars. Free sugars are those added to foods by the manufacturer, cook or consumer and sugars naturally present in honey, syrups and fruit juices.
The evidence was less consistent in children, mainly due to poor compliance with dietary advice. However, for sugar-sweetened beverages such as soft drinks, the risk of being overweight or obese increased among children with the highest intake of sugary drinks compared with those with the lowest intake.
The authors of the research, led by research fellow Dr Lisa Te Morenga and Professor Jim Mann, conclude that, while obesity has many causes, “when considering the rapid weight gain that occurs after an increased intake of sugars, it seems reasonable to conclude that advice relating to sugars intake is a relevant component of a strategy to reduce the high risk of overweight and obesity in most countries”.
Listen to this Radio NZ Our Changing World programme: Sugar: Desirable But Deadly which features Lisa Te Morenga.
When we eat: early eaters lose more
Researchers from the University of Murcia in Spain found that, when you eat your main meal of the day (this is lunch for the Mediterranean populace who participated in this study) can have an impact on dieting. A study of 420 participants in a weight-loss programme found that those who ate later in the day (after 3.00pm) lost less weight at a slower rate than early eaters (before 3.00pm) over a 20-week course.
The researchers noted that, while energy intake, dietary composition, estimated energy expenditure, appetite hormones and sleep duration were similar between both early eaters and late eaters, they found that late eaters were more active in the evenings, had less energetic breakfasts and skipped breakfast more frequently that early eaters. They concluded that eating late can adversely influence the success of weight-loss therapy and advised that such therapies “should incorporate not only the caloric intake and macronutrient distribution – as is classically done – but also the timing of food”.
The research was published in the International Journal of Obesity.
How we eat: small bites
Previous research shows that eating while distracted, such as watching TV, can make people eat more without realising. More research published in the journal PLoS ONE shows that reducing bite sizes may be able to counter this effect.
The study by researchers from Wageningen University in the Netherlands examined the effects of controlling mouthful size in an eating experiment where participants were distracted by a film.
In the experiment, 53 healthy subjects consumed as much soup as they wanted with small sips (5 g, 60 g/min), large sips (15 g, 60 g/min) and free sips (where sip size was determined by subjects themselves) in both a distracted and a focused state. Sips were administered via a pump, with no visual cues about how much they were eating. Subjects then had to estimate how much they had consumed by filling soup in soup bowls.
The authors found that people who ate pre-specified small bites/sips of food consumed about 30% less than those who had to consume large sips or had no eating restrictions. In addition, people who took large sips, which were either fixed or chosen by subjects themselves, tended to underestimate the amount they consumed, indicating that large bite size is a risk factor for over-consumption. The authors concluded that reducing the size of your mouthful does indeed reduce how much you eat, even if you are eating when distracted.
Your students may like to view this video clip Adolescent diet in which Carolyn Cairncross, a nutritionist with the New Zealand Nutrition Foundation, describes some of the key components of the adolescent diet. Your students could go on to discuss whether this recommended diet may be affected by the new research findings described in this news article.