Last month one of my blogs focused on the evidence which shows that exercise is, generally speaking, really quite ineffective for the purposes of weight loss. That is not to say that there’s nothing to be said for exercise. It is, for example, linked with a reduced risk of chronic and potentially fatal conditions such as cardiovascular disease and type 2 diabetes. Regular activity is also linked to enhanced longevity, . have benefits for the brain. As I concluded last month’s blog post, there are plenty of good reasons to exercise, it’s just that weight loss isn’t one of them.
The notion that exercise might have benefits for health, even in the absence of weight loss, was reinforced by a study published in the journal Obesity . In this study, 29 children and adolescents (average age 15) were put on a programme of exercise over a 12-week period. The study subjects exercised for 30 minutes, four times a week at 70 per cent maximum capacity (this would equate to a heart rate of about 140). About half the study participants were obese at the start of the study, while the rest were ‘lean’.
The study participants were assessed for a number of parameters, including fitness, fat levels in the muscles and liver, and insulin sensitivity (the ability for insulin to do its job). The exercise intervention did not lead to weight loss. Lean individuals did not see any significant benefit in the parameters listed above apart from fitness. However, for obese individuals, the story was different. Here, changes included:
1. reduced fat levels in the liver
2. reduced levels of insulin in the fasting state
3. improved insulin sensitivity
These changes, particularly in conjunction with enhanced fitness, would be generally taken signs of an improved metabolic state likely to translate into a reduced risk of chronic diseases such as cardiovascular disease and type 2 diabetes.
This study shows how it is possible for exercise to bring benefits for the body, even in the absence of weight loss. However, in this study, short-term metabolic benefits appeared to be confined to obese, rather than lean, individuals.
1. van der Heijden GJ, et al. Hepatic Fat Accumulation and Insulin Resistance in Obese, Hispanic Adolescents. Obesity 20th August 2009 [epub ahead of print publication]