The effect of exercise in weight loss appears to be very different depending on individual. In my case it is an important component for weight loss and maintenance - exercise or diet by themselves don't cut it.
A paper in the British Journal of Sports Medicine focuses on individual variability (behind their paywall)
Exercise, appetite and weight management: understanding the compensatory responses in eating behaviour and how they contribute to variability in exercise-induced weight loss
N A King1, K Horner1, A P Hills1, N M Byrne1, R E Wood1, E Bryant2, P Caudwell3,G Finlayson3, C Gibbons3, M Hopkins4, C Martins5, J E Blundell3
- 1Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
- 2Centre for Psychology Studies, University of Bradford, Bradford, UK
- 3BioPsychology Group, Institute of Psychological Sciences, University of Leeds, Leeds, UK
- 4Department of Sport, Health, Leisure and Nutrition, Leeds Trinity University College, Leeds, UK
- 5Obesity Research Group, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
- Correspondence toN A King, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane 4059, Australia; firstname.lastname@example.org
- Accepted 13 April 2011
- Published Online First 19 May 2011
Does exercise promote weight loss? One of the key problems with studies assessing the efficacy of exercise as a method of weight management and obesityis that mean data are presented and the individual variability in response is overlooked. Recent data have highlighted the need to demonstrate and characterise the individual variability in response to exercise. Do people who exercise compensate for the increase in energy expenditure via compensatory increases in hunger and food intake? The authors address the physiological, psychological and behavioural factors potentially involved in the relationship between exercise and appetite, and identify the research questions that remain unanswered. A negative consequence of the phenomena of individual variability and compensatory responses has been the focus on those who lose little weight in response to exercise; this has been used unreasonably as evidence to suggest that exercise is a futile method of controlling weight and managing obesity. Most of the evidence suggests that exercise is useful for improving body composition and health. For example, when exercise-induced mean weight loss is <1.0 kg, significant improvements in aerobic capacity (+6.3 ml/kg/min), systolic (−6.00 mm Hg) and diastolic (−3.9 mm Hg) blood pressure, waist circumference (−3.7 cm) and positive mood still occur. However, people will vary in their responses to exercise; understanding and characterizing this variability will help tailor weight loss strategies to suit individuals.
and Alex Hutchinson offers some commentary on Sweat Science.
...one of the big themes is individual variability. To illustrate the point, check out this graph:
This shows the individual weight-loss results for 58 men (filled bars) and women (open bars) after 12 weeks of supervised exercise, designed to burn 500 calories per session five times a week. On average, the weight loss was pretty mediocre: 3.2 kg. But the scatter of results is pretty dramatic: some people lost more than 10 kg, while others actually gained weight, despite performing essentially identical exercise routines! This is significant. Exercise clearly worked to lose weight for some (but not all) of the subjects. The question is: why?
Again, it's clear that the exercise program somehow spurred positive changes among some people but not among others. The overall message here definitely isn't that exercise is a magic bullet for weight loss -- it's a reminder that (a) obesity likely results from a variety of factors, and (b) the exact combination of factors is different in each person. For some people, lack of exercise is clearly not their underlying problem, so adding exercise isn't going to help*. For others, adding exercise could be a crucial ingredient to help them lose weight.
For me it became clear that a mixed approach was necessary. I journal all exercise and meals and have five sessions of ~700kcal aerobic exercise five times a week. My body was unresponsive to diet or exercise alone, hoping that a self regulation mechanism would kick in. The maintenance phase is, if anything, more difficult than weight loss and some vigilance is going to be necessary on the long term. The critical piece is - at least for me (an anecdotal data point with a sample size of one) - that regulation is somehow easier with the mixture of exercise and diet control. Additionallly there are added benefits from the exercise, so it just makes sense.