Obese women following a strictly controlled diet and intermittent fasting (IF) lose the most weight and enjoy improvements in their overall health when compared to several other diets, research from the University of Adelaide says. The study, published in the journal Obesity, involved a sample of 88 women following carefully controlled diets for over ten weeks. The researchers note that further research is warranted to see if these short-term results translate into the long-term.
“In our two-month study, we observed greater improvements in cardiovascular and diabetes risk markers following IF vs. a daily caloric restriction diet (CR) that was prescribed at matched energy restriction,” co-author, Professor Leonie Heilbronn, Ph.D. from the University of Adelaide, tell.
The study participants were overweight or obese women with a Body Mass Index (BMI) in the 25-40 range and aged between 35-70 years. The women followed a typical Australian diet consisting of 35 percent fat, 15 percent protein and 50 percent carbohydrate. The most successful participants lost roughly half to one kilogram per week.
According to the researchers, obese women who followed a diet in which they ate 70 percent of their required energy intake and fasted intermittently lost the most weight.
Participants who fasted intermittently ate breakfast and then refrained from eating for 24 hours followed by 24 hours of eating. The following day they fasted again.
“Other women in the study who either fasted intermittently without reducing their food intake, reduced their food intake but did not fast, or did not restrict their diet at all, were not as successful in losing weight,” says the study’s lead author, Dr. Amy Hutchison of the University of Adelaide.
“We are now conducting a follow-up study to determine the long term sustainability of IF,” Heilbronn adds.
Studies have shown that obese women who followed CR diets had trouble in maintaining this way of eating in the long term.
The study also found that women who fasted intermittently, as well as restricting their food, saw improvements in other markers of health compared to those who only restricted their diet or only fasted intermittently.
“By adhering to a strict pattern of intermittent fasting and dieting, obese women achieved significant weight loss and improvements in their health such as decreased markers for heart disease,” says Dr. Hutchison.
“This study is adding to evidence that intermittent fasting, at least in the short term, may provide better outcomes than daily continuous diet restriction for health and potentially, for weight-loss,” notes Heilbronn.
“Energy metabolism is reduced by daily calorie restriction and we see similar reductions with intermittent fasting. Pre-clinical studies of IF do show positive effects on energy metabolism. But we have not detected this in humans,” she adds.
While the study confirms that intermittent fasting is more effective than continuous diet restriction, the underlying signal for limiting people’s appetite, which could hold the key to triggering effective weight loss, requires further research, the researchers say.Professor Heilbronn says that some women did really well with CR and some women did not do well with IF. “We have looked to see if we can find predictors of who should follow which diet but have not found anything definitive as yet.”
The team is now conducting more research to further understand the effects of IF. “We are studying the comparative effects of IF vs. CR over 18 months in men and women with pre-diabetes,” says Heilbronn
“We are also studying the effects of time restricted eating (limiting intake to 10 hours (8am-6pm) every day. We have just had an acute study accepted for publication which should be coming out shortly. We are now doing longer-term trials of that too,” she concludes.
Proponents of IF claim that it can improve blood sugar levels, decrease the risk of heart disease, stroke and cancer, prevent or delay the onset of neurodegenerative diseases and even improve memory, mood and depression.
With such an extensive list of benefits, one could argue that no wonder the diet has reached such fashionable heights. In order to provide stable scientific backing to IF, a series of systematic scientific reviews have been conducted.
One review found that IF paired with moderate aerobic exercise may enhance endurance. While another study discovered that IF clears fat from the blood quicker after eating meals than daily calorie restriction diets – reducing an important risk factor for cardiovascular disease.
NutritionInsight has previously reported on IFand its increasing popularity that rendered it a 2018 trending diet, spawning variations.
“IF is an umbrella term encompassing a range of diets where the pattern of calorie restriction and/or timing of food intake are altered so that the individuals undergo frequently repeated periods of fasting,” Dr. Samefko Ludidi, Food and Health consultant, and researcher at Maastricht University said.
Many of the latest diets and trends are based upon variations of IF, for example, the 5:2 diet (normal consumption five days a week and restricted calories two days a week), the warrior diet (eating small amounts of raw fruits and vegetables during the day and one large meal at night) and the CSIRO “Flexi” diet.