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Physical activity not linked with weight change in African-origin adults

An international study of young adults from South Africa, Ghana, the US, Jamaica and the Seychelles found that neither physical activity nor sedentary time were associated with weight gain.

"Our study results indicate that physical activity may not protect you from gaining weight," said lead author Dr Lara R Dugas, an assistant professor in the department of public health sciences of Loyola University Chicago Stritch School of Medicine.

Physical activity has many proven health benefits, ranging from reducing the risk of heart disease, diabetes, and cancer to improving mental health and mood. People who are physically active tend to be healthier and live longer. But while physical activity burns calories, it also increases appetite, and people may compensate by eating more or by being less active the rest of the day.

Some experts have suggested that a decline in physical activity, especially in the workplace, has been a key contributor to the obesity epidemic. But research such as the new Loyola study, in which physical activity is objectively measured and participants are followed over time, has not found a meaningful relationship between weight gain and physical activity.

The Loyola study is one of the primary outcomes of the Modeling the Epidemiologic Transition Study (METS). In METS, researchers followed adults aged 25 to 40 living in five countries: the US, Ghana, South Africa, Jamaica and Seychelles (an island country east of Africa).

The US adults live in Maywood, Illinois, a suburb of Chicago. Participants are predominantly of African descent and represent a broad range of social and economic development. Principal investigator of METS and senior author of the Loyola study is Amy Luke, professor and vice chair of Loyola's department of public health sciences.

Previous research has found that when people are asked about their physical activity, they tend to overstate the amount they do. To provide a more objective measure, participants wore tracking devices called accelerometers on their waists for a week. The devices measured the wearers' energy expenditure and step count. Researchers also measured participants' weight, height and body fat. After an initial exam, participants were asked to return one year and two years later.

At the initial visit, Ghana participants had the lowest average weights (139 pounds for both men and women), and Americans the highest weights (202 pounds for women, 206 pounds for men). Ghanaians also were fitter than Americans – 76% of Ghanaian men and 44% of Ghanaian women met the US surgeon general physical activity guidelines, while only 44% of American men and 20% of American women met the guidelines. The guidelines recommend doing at least two and a half hours of moderate-intensity aerobic exercise (such as brisk walking) per week.

Surprisingly, total weight gain in every country was greater among participants who met the physical activity guidelines. For example, American men who met the guidelines gained a half pound per year, while American men who did not meet the guideline lost 0.6 pounds.

Researchers did not find any significant relationships between sedentary time at the initial visit and subsequent weight gain or weight loss. The only factors that were significantly associated with weight gain were weight at the initial visit, age and gender.

Abstract
Background: Increasing population-levels of physical activity (PA) is a controversial strategy for managing the obesity epidemic, given the conflicting evidence for weight loss from PA alone per se. We measured PA and weight change in a three-year prospective cohort study in young adults from five countries (Ghana, South Africa, Jamaica, Seychelles and USA).
Methods: A total of 1,944 men and women had baseline data, and at least 1 follow-up examination including measures of anthropometry (weight/BMI), and objective PA (accelerometer, 7-day) following the three-year study period. PA was explored as 1-minute bouts of moderate and vigorous PA (MVPA) as well as daily sedentary time.
Results: At baseline; Ghanaian and South African men had the lowest body weights (63.4 ± 9.5, 64.9 ± 11.8 kg, respectively) and men and women from the USA the highest (93.6 ± 25.9, 91.7 ± 23.4 kg, respectively). Prevalence of normal weight ranged from 85% in Ghanaian men to 29% in USA men and 52% in Ghanaian women to 15% in USA women. Over the two-year follow-up period, USA men and Jamaican women experienced the smallest yearly weight change rate (0.1 ± 3.3 kg/yr; −0.03 ± 3.0 kg/yr, respectively), compared to South African men and Ghanaian women greatest yearly change (0.6.0 ± 3.0 kg/yr; 1.22 ± 2.6 kg/yr, respectively). Mean yearly weight gain tended to be larger among normal weight participants at baseline than overweight/obese at baseline. Neither baseline MVPA nor sedentary time were associated with weight gain. Using multiple linear regression, only baseline weight, age and gender were significantly associated with weight gain.
Discussion: From our study it is not evident that higher volumes of PA alone are protective against future weight gain, and by deduction our data suggest that other environmental factors such as the food environment may have a more critical role.

Authors
Lara R Dugas, Stephanie Kliethermes, Jacob Plange-Rhule, Liping Tong, Pascal Bovet, Terrence E Forrester, Estelle V Lambert, Dale A Schoeller, Ramon A Durazo-Arvizu, David A Shoham, Guichan Cao, Soren Brage, Ulf Ekelund, Richard S Cooper, Amy Luke

[link url="https://www.sciencedaily.com/releases/2017/02/170203163857.htm"]Loyola University Health System material[/link]
[link url="https://doaj.org/article/b312c6edf0fa4f0285420f27cbe89fc4"]Peer J abstract[/link]

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