In the last few decades, there has been a strong interest in effective weight gain prevention strategies to combat rising obesity prevalence (Armstrong et al, 2011, Brown et al, 2009, Cavill et al, 2012, Franz et al, 2007, Greaves et al, 2011, Neve et al, 2010, Young et al, 2012). Not surprisingly, the worldwide weight gain trend correlates with decreasing levels of adherence to population diet and physical activity recommendations (Australian Bureau of Statistics, 2009, King et al, 2009). Behavioural treatments that incorporate diet and physical activity lifestyle changes are recommended for weight control interventions (Dietitians Association of Australia, 2005, Lau et al, 2007, Tsigos et al, 2008). Weight loss interventions have had small yet clinically important effects (Franz et al, 2007, Greaves et al, 2011, Neve et al, 2010, Young et al, 2012); however, few interventions have been successful in facilitating weight loss beyond two years (Barte et al., 2010).
In addition to evaluating whether an intervention is effective, it has been recognised that understanding how interventions achieve their results is important (Baranowski, 2006). Understanding how ‘successful’ intervention participants achieve weight loss provides insight into effective weight control treatment (Teixeira et al., 2009). Mediation analysis is emerging as an important statistical tool in weight loss research as it provides evidence on the mechanism of change in a behavioural intervention (Lockwood, DeFrancesco, Elliot, Beresford, & Toobert, 2010). This provides an opportunity for researchers to understand associations between complying with diet, physical activity and sedentary behaviour recommendations and achieving weight loss (Lubans et al., 2012). Determining which intervention recommendations are more effective will enable the development and refinement of more targeted weight management programs (Hultquist et al, 2005, Swinburn et al, 2004) and will enable researchers to modify intervention resources to support recommendations that are associated with weight loss success (Teixeira et al., 2009).
The ‘40-Something’ Randomised Controlled Trial (RCT) aimed to determine whether a 12-month health professional-led intervention, employing motivational interviewing as the counselling framework, could result in diet and physical activity behaviour change for weight control in non-obese, premenopausal mid-age women (Williams, Hollis, Collins, & Morgan, 2013). Weight gain prevention advice for all participants was based on 10 weight control recommendations. Seven recommendations related to dietary intake for vegetable, fruit, meat, dairy, wholegrains and extra (non-discretionary food) serves as well as the number of meals eaten outside the home. Two recommendations related to physical activity for minutes of moderate-to-vigorous physical activity and step count, and one to sedentary behaviour (Box 1). This paper aimed to examine whether compliance to the 10 weight control recommendations of the 40-Something study significantly mediated the long-term effect of the intervention on weight loss at 12 and 24 months. The 40-Something study methods paper (Williams et al., 2013) and the 12-month weight outcomes paper (which also presents the waist circumference, percentage body fat, percentage lean muscle mass, blood cholesterol level, fasting glucose and blood pressure findings) (Williams, Hollis, Collins, & Morgan, 2014) have been published. This paper presents the findings from our mediation analysis to determine how successful intervention women achieved weight gain prevention and provides evidence of the mechanism of behaviour change.The 10 weight control recommendations provided to both Motivational Interviewing and Self-Directed Intervention participants.
- 1.
Aim to eat at least 2 serves of fruit every day, where 1 serve is 1 medium piece of fruit, 2 small pieces of fruit, 1½ tablespoons of sultanas, 4 dried apricot halves or ½ cup fruit juice.
- 2.
Aim to eat at least 5 serves of vegetables every day, where 1 serve is ½ cup cooked vegetables or 1 cup raw salad vegetables.
- 3.
Aim to eat 1–1½ serves of meat or meat alternatives every day, where 1 serve is 65–100 g cooked meat or chicken, 120 g cooked fish fillet, 2 eggs, ½ cup cooked beans, lentils, chickpeas or canned beans, 1/3 cup nuts or ¼ cup sunflower seeds or sesame seeds.
- 4.
Aim to eat 2–3 serves dairy every day, where 1 serve is 250 ml milk (fresh or long life cow milk or soy milk), 125 ml evaporated milk, 200 g yoghurt, 40 g cheese or 2 slices pre-sliced cheese.
- 5.
Aim to eat wholegrain varieties of breads and cereal. Wholegrain varieties are recommended as they may assist in avoiding weight gain.
- 6.
Limit your intake of extra foods which are high in fat and sugar, to 2 serves per day (or 1.5 for weight loss) or less. One serve of extra food is 1 doughnut, or 4 plain sweet biscuits, 1 slice of cake, ½ small chocolate bar, 2 tablespoons cream or mayonnaise, 1 tablespoon of oil, butter or margarine, 200 ml wine or 60 ml spirits, 600 ml light beer, 400 ml beer, 1 can of soft drink, 1 small packet crisps, 2/3 slice of pizza, 1/3 meat pie or pastry, 12 hot chips or 1½ scoops ice-cream.
- 7.
Aim to cut down on the number of meals eaten outside the home each week, as these foods are often higher in fat, sugar and salt.
- 8.
Aim to engage in moderate to vigorous physical activity for 150 minutes (or 250 minutes for weight loss) total per week. Activities may include brisk walking, jogging, exercise classes, sports, swimming, dancing, cycling or vigorous household chores.
- 9.
Aim to sit for less than 3 hours each day.
- 10.
Aim to walk 10,000 steps per day by being active in as many ways as possible. Try walking to work, taking the stairs instead of the lift, walking to the shops for your newspaper or milk on the weekend or challenging family and friends to be active with you.