Acute and Chronic Effects of Exercise on Appetite, Energy Intake, and Appetite-Related Hormones
The simple equation for obesity is Energy out < Energy in. The simplest way of increasing our ‘Energy out’, is to exercise more. However, the benefits of exercise extend beyond just calories, and in fact, it’s thought that exercise can improve subjective and homeostatic mediators of appetite in directions associated with enhanced meal-induced satiety. The degree to which this effect exists in an individual is highly variable and difficult to predict. This review, published in Nutrients, seeks to understand how adiposity, sex, and habitual physical activity modulate exercise-induced appetite, energy intake, and appetite-related hormone responses.
The review found that changes in perceptions of appetite, energy intake, and macronutrient composition in response to acute and chronic exercise stimuli are not modulated by levels of body adiposity or sex. However, in individuals with higher levels of habitual physical activity, they may exhibit improved sensitivity of the appetite control system through better compensatory adjustments for the energy content and density of food.
Although not conclusive, this paper draws attention to the benefits of exercise and need for an improved understanding of the individual factors that modulate appetite, appetite-related hormones, and food intake. Responses to exercise may help to explain the individual variability in body weight changes, and to facilitate the development of more efficacious weight management interventions.
Read MoreA long-term maternal diet intervention to avoid the obesogenic effect in the offspring
The American Heart Association states that obesity among girls and women has generated a vicious cycle that contributes to the obesity epidemic. Studies into maternal overnutrition have found that high-fat diets in humans (which reflects the western diet), whereby the baby is exposed to over-nutrition during gestation, have increased risks of obesity, diabetes and other complications. In this study, published in The Journal of Nutritional Biochemistry, the diets of pregnant mice are varied to see whether they can prevent obesity related disease in the offspring, regardless of the weight-management of the mother.
The researchers transitioned the mice to normal fat (NF) diet 1 week, 5 weeks and 9 weeks before conception and continued this throughout gestation and lactation. After this, the offspring were given a high-fat diet for 12 weeks then sacrificed. They found that the mice whose parent had the NF diet for 9 weeks had a reduced risk of obesity, diabetes and other complications, regardless of maternal weight, suggesting a metabolic memory in the offspring that can be improved. Although the metabolic profiles of mice and humans are vastly different, the ease of access and economy of lifestyle interventions mean that a strategy to improve maternal diet for a period before conception, may be able to help prevent multi-generational obesity.
Read MoreEating faster is associated with general and abdominal obesity among Chinese children
Eating faster results in an increased rate of energy intake. However, the relationship between children’s eating speed, food intake and general abdominal adiposity is unknown, and forms the basis of this paper. A total of 50,037 Chinese children aged 7-17 years were enrolled from 7 provinces in China in 2013. Objective measurements of anthropometrics were taken and food speed was assessed by questionnaire.
There was a significant increasing trend across the slow, medium, and fast eating speed groups observed, in the prevalence of general obesity (7.2%, 10.0% and 15.9%), abdominal obesity (16.1%, 21.8%, and 29.4%) and waist-to-height ratio (WHtR) ≥ 0.5 (11.1%, 14.8%, and 22.0%). Compared with medium eating speed, fast eating speed was positively associated with obesity, abdominal obesity, and WHtR ≥ 0.5, while slow eating speed was negatively associated with these outcomes. They also found increased speed was associated with increased consumption.
Although this paper doesn’t tell us anything of the mechanism of this phenomenon, there are several biologically plausible suggestions. Such as, fast-eating leads to lower satiety and higher calorie intake, while slow-eating leads to enhanced thermic effect of food and also influences the release of gastrointestinal satiety hormones. More research should be done to see if it’s possible to change eating speed in adults, and whether this has any effect on obesity, as this could provide a simple non-invasive therapeutic target.
Read MoreImpact of overweight, obesity and severe obesity on life expectancy of Australian adults
Obesity is known to significantly elevate the risk of many health problems, however its impact on life expectancy (LE) has not been quantified in Australia. This paper, published in the International Journal of Obesity, uses a microsimulation model of obesity progression to predict the changes in LE and years of life lost (YLL). It uses data on annual change in BMI based on age and sex, with Australian life-table data and published relative risk of all cause-mortality for different BMI categories. A nationally representative sample of 12,091 adults aged 20-69 were used.
The study predicted that the loss in LE for obese people to be 5.6-7.6 years and for severely obese people to be 8.1-10.3 years for men and women aged 20-29 years. If the baseline BMI was higher, so at age 20-29 BMI was above 25, years lost was greater. It also found that men lost 27.7% more years compared to women. In total, overweight and obesity was predicted to be responsible for 36.3 million YLL over the life course, with the severely obese contributing almost one-third of the life years lost despite comprising only 11% of the population.
This study does not take into account the impact that increased BMI has on quality-of-life, however evidence has shown there are significant impairments to health related quality-of-life for individuals at more severe levels of obesity as a result of co-morbidity and disability. This paper highlights the huge burden of disease in Australia, particularly in men, that needs to be addressed. The implication on the economy and the individual of 36.3 million YLL are too huge to ignore.
Read MoreAnalysis of the impact of rising food prices on obesity in women across 31 low and middle-income countries
In this longitudinal study, published in the International Journal of Obesity, the authors examine whether changes in food prices are associated with changes in obesity prevalence among women in developing countries, and assess the effect of individual socioeconomic status (SES). Anthropometric data, including BMI, and country-level food price inflation from low and middle income countries (LMIC) was used from 296,000 non-pregnant adult women, over the period 2000 to 2014.
The researchers found a strong link between food price inflation and obesity in adult women in LMICs, and the relationship is consistently modified by individual SES. Regardless of indicator used, higher food price inflation was positively associated with obesity among women in top SES categories, but was flat or negative among women in low SES categories, averaging over time. In lower SES groups it’s hypothesized that this is a result of a relative lack of exposure to food pricing, due to them growing their own food. Educational differences appeared the strongest of all SES measures which is consistent with the literature on social determinants of obesity.
This response to food budget constraints is recognised by other comparisons of LMICs, showing that individuals greatly reduce fruit and vegetable intakes as the relative cost increases [2], and that only those in the highest socioeconomic groups increase caloric intake in response to rising food prices. As the international burden of obesity grows, it’s important to understand how economic fluctuations translate into behavioural changes
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