Combined diet and exercise changes improve body measurements and heart health more than changes in diet or exercise alone

Schwingshackl L, Dias S, Hoffmann G. Impact of long-term lifestyle programmes on weight loss and cardiovascular risk factors in overweight/obese participants: A systematic review and network meta-analysis Systematic Reviews. 2014;3:130.

Review question

How do long-term changes in diet and exercise affect anthropometric measures (body measurements such as weight and amount of body fat) and cardiovascular health in people who are overweight or have obesity?

Background

People who are overweight or obese are especially at risk for diseases of the heart or blood vessels, also known as cardiovascular disease (CVD). Exercise and a healthy diet help to prevent and treat overweight and obesity. This study compared the impact of long-term changes in diet, exercise, and/or a combination of diet and exercise on body measurements and cardiovascular health.

How the review was done

This systematic review included 21 randomized controlled trials published between 1988 and 2013. The studies involved a total of 3,521 overweight participants with an average age ranging from 35-70 years. 680 participants had type 2 diabetes. The studies compared the effect of changes in:

• diet vs. a combination of diet and exercise (17 studies)
• exercise vs. a combination of diet and exercise (11 studies)
• diet vs. exercise (14 studies)

The length of the programs ranged from 12 to 72 months including follow-up. The diet programs recommended low-fat foods as well as eating more fruits, vegetables and fibre. The exercise programs included a ‘prescription’ for regular exercise, including both aerobic (e.g. walking) and resistance exercises. Some of the studies included supervision of the exercise and monitoring of heart rate.

Body measurements (such as waist circumference, weight, and amount of body fat) and measures of cardiovascular health (such as fitness, blood pressure and cholesterol levels) were compared before and after the study period.

What the researchers found

Combined diet and exercise changes improved:

• weight and amount of body fat compared to diet changes alone
• weight, amount of body fat and waist measurements compared to exercise changes alone
• blood pressure and blood lipids compared to either diet or exercise changes alone

Changes in diet led to greater improvements in body weight and amount of body fat than a change in exercise.  

Conclusion

Changing both diet and exercise improves weight, body measurements and cardiovascular health more than changes in diet or exercise alone for people who are overweight.  A change in diet alone improves weight and body fat percentage more than a change in exercise alone.