title: Physical activity and healthy diet: determinants and implicit relationship.
abstract: OBJECTIVE
  People who decide to lose weight by dieting often do so without participating in any associated physical activity. Although some people who participate in sports are unconcerned about their diet, it is generally believed that people who exercise tend to eat a healthy diet and those who do not exercise eat a less healthy diet. There is no clear relationship between the decisions regarding participation in physical activity and eating a healthy diet when choices are taken freely and not influenced by policy factors promoting healthy behaviour. However, these decisions may reveal some common explanatory factors and an implicit link. As such the aim of this study was to identify the common explanatory factors and investigate the existence of an implicit relationship.
  
  
  METHODS
  Econometric estimate - bivariate probit estimation.
  
  
  METHODS
  Using data from the Portuguese National Health Survey, a bivariate probit was undertaken for decisions regarding participation in physical activity and eating a healthy diet. The correlation between the residuals gives information on the implicit relationship between the healthy choices.
  
  
  RESULTS
  Common explanatory factors were found between the decisions to eat healthy snacks and participate in physical activity, such as being married. However, holding voluntary private health insurance, smoking, getting older, living alone and unemployment were found to dissuade people from making healthy choices. Positive correlation was found between the residuals of the probit estimations, indicating that other unmeasurable variables have a similar influence on both decisions, such as peer pressure, cultural values, fashion, advertising and risk aversion.
  
  
  CONCLUSIONS
  Further research is needed to improve understanding of decision making related to participation in physical activity and eating a healthy diet. This will facilitate the design of policies that will make a greater contribution to healthy lifestyles.
authors.affiliation: CEISUC, University of Coimbra, Coimbra - Portugal and DEGEI, University of Aveiro, Aveiro, Portugal. Electronic address: aitavar@gmail.com.
authors.forename: Aida Isabel
authors.initials: AI
authors.lastname: Tavares
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003657:Decision Making; D004032:Diet / Q000523:psychology* / Q000706:statistics & numerical data; D015444:Exercise / Q000523:psychology*; D005260:Female; D015438:Health Behavior; D006306:Health Surveys; D006801:Humans; D007348:Insurance, Health / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011174:Portugal; D012907:Smoking / Q000523:psychology; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: Bivariate probit; Correlation; Determinants; Exercise; Snacks