Posted by: Chris Maloney | January 7, 2013

Weight Loss : Diet Or Diet Plus Exercise?

Diet and Nutrition

Diet and Nutrition (Photo credit: fantasyhealthball)

Anyone who knows me hears the mantra:  it’s hormones, hormones, hormones.

But I know I’m preaching to a sweaty, hungry crowd, so let’s answer that big, big question.  If I’m dieting, will exercise help me lose weight?

Short answer is yes.  Read on if you want to stay clear of the gym.  Skip down to the bold if you have a degree in statistics.

When we study diet and exercise, we do studies.  Dieters are enrolled by researchers and followed by those researchers.

Many studies are flawed, like the one I heard advertised on the radio today.  Green coffee bean extract makers were hiring people to give weight loss testimonials.  So they enrolled them in a study, paying them for extra pounds lost on green coffee bean extract.  I don’t know about you, but I won’t be paying that study a great deal of attention when it’s published.

But a lot of studies aren’t as obvious.  People are generally enrolled in two branches of a study and researchers see how they did.  At this point we’ve done so many studies that statistical researchers do a meta-analysis of all the studies and tell you what all the studies come up with if they are pooled together in a bunch.  There are problems with doing this, and statisticians end up in a lot of drunken bar fights over how to do it right, but it’s the best thing we’ve got in medicine at this point.

So when I say that exercising will help you lose weight, I’m quoting a meta-analysis done by Harvard researchers on all the weight loss studies.  The additional weight loss they found from adding exercise to dieting was (drum roll please) 1.14 kg.  For us metrically impaired folks we multiple kg by 2.2 to get:  2.5 lbs.  Researchers also pointed out that this weight loss benefit continued in longer studies of over two years.

If some of you are nonplussed by the “significantly greater weight loss” given to you by adding exercise, join the club.  I generally see patients who want to lose thirty or forty pounds, and who won’t be particularly pleased with me for making them sweat every day on a treadmill for a couple of pounds extra.  What I can say is that individualizing weight loss programs to accommodate hormonal needs is far more effective.  My own record weight gain is eight pounds in a single day and sixteen pounds in a weekend, all of which was lost in the following week.

Here’s the study abstract from Harvard (link here):

Obes Rev. 2009 May;10(3):313-23. doi: 10.1111/j.1467-789X.2008.00547.x. Epub  2009 Jan 19.

Long-term effectiveness of diet-plus-exercise interventions vs. diet-only interventions for weight loss: a meta-analysis.


Department of Nutrition, Harvard School of Public Health, Boston, MA, USA.


Diet and exercise are two of the commonest strategies to reduce weight. Whether a diet-plus-exercise intervention is more effective for weight loss than a diet-only intervention in the long-term has not been conclusively established. The objective of this study was to systemically review the effect of diet-plus-exercise interventions vs. diet-only interventions on both long-term and short-term weight loss. Studies were retrieved by searching MEDLINE and Cochrane Library (1966 – June 2008). Studies were included if they were randomized controlled trials comparing the effect of diet-plus-exercise interventions vs. diet-only interventions on weight loss for a minimum of 6 months among obese or overweight adults. Eighteen studies met our inclusion criteria. Data were independently extracted by two investigators using a standardized protocol. We found that the overall standardized mean differences between diet-plus-exercise interventions and diet-only interventions at the end of follow-up were -0.25 (95% confidence interval [CI]-0.36 to -0.14), with a P-value for heterogeneity of 0.4. Because there were two outcome measurements, weight (kg) and body mass index (kg m(-2)), we also stratified the results by weight and body mass index outcome. The pooled weight loss was 1.14 kg (95% CI 0.21 to 2.07) or 0.50 kg m(-2) (95% CI 0.21 to 0.79) greater for the diet-plus-exercise group than the diet-only group. We did not detect significant heterogeneity in either stratum. Even in studies lasting 2 years or longer, diet-plus-exercise interventions provided significantly greater weight loss than diet-only interventions. In summary, a combined diet-plus-exercise programme provided greater long-term weight loss than a diet-only programme. However, both diet-only and diet-plus-exercise programmes are associated with partial weight regain, and future studies should explore better strategies to limit weight regain and achieve greater long-term weight loss.


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