Quick Hit Summary
Exercise is an important part of weight loss. Recent research indicated that the combination of decreasing caloric intake (12.5%) and increasing caloric expenditure (12.5%) was just as effective as drastic reductions in kcal intake (25%) with respect to weight loss. Besides assisting with weight loss, the exercise group acquired significant improvements in cardiometabolic risk factors including decreased diastolic blood pressure (-5%), LDL cholesterol (-13%), total cholesterol (-9%), improved insulin sensitivity (+66%) and increased HDL cholesterol (+10%). Of these variables, the reduced caloric intake group ONLY saw significant improvements in HDL cholesterol levels.
Exercise and Weight Loss
Figure 1 Has a little moss grown over your rock hard abs?8
Weight loss… it seems that every individual over the age of 30 would like to drop a few pounds. Although I haven’t seen any gallup polls on the subject, I’m sure that one of the top New Year resolutions is, “I’d like to lose weight (5-15+ lbs) lbs this year.” However, the question exist, “What is the best way to lose weight?” More exercise is generally considered to be one of the answers to this question. However, in August, 2009, a highly controversial article was published in Time Magazine in which the writer, John Cloud, argued that exercise was kind of a waste of time if one’s goal was to lose weight1. In support of this argument, he points to research indicating that weight loss did not vary amongst overweight women who exercised for various amounts of time. He then goes on to discuss that when individuals exercise, they are more likely to eat a doughnut or candy bar vs. healthier options. So is exercise even a useful addition to a weight loss program, or is dietary modification alone enough for weight loss?
Recent Research on Exercise and Weight Loss
In a recently published study, Larson-Meyer et al. sought to find how decreasing caloric intake, with or without aerobic exercise, affected body composition and cardiometabolic risk factors in 36 overweight men and women (25+<+BMI<30; age- 25-50)2. To be included in the study, all participants had to be free of cardiovascular disease, high blood pressure, diabetes and not currently taking any medications. For 6 months, study participants were randomly assigned to either a caloric restriction group (CR) (decrease baseline caloric intake by 25%), exercise + caloric restriction group (ECR) (increase caloric expenditure by 12.5% + decrease baseline caloric intake by 12.5%) or a control group (weight maintenance). All diets were in accordance to the American Heart Associations Step 1 recommendations. As seen above, the ERC and RC groups were designed such that the total fluctuation of calories (decreased kcal intake + increased kcal expenditure) was equal between both groups.
Exercise Protocol
Each individual exercised 5 days per week. The average exercise time was 53 minutes/session for the women, burning a ~403 kcal/session, and 45 minutes for the men, who burned ~569 kcal/session. Participants were able to choose both the mode of aerobic exercise (ie- walking, bicycling, etc) and training intensity. Researchers only set the time length of each session to ensure that each individual met the energy expenditure requirements.
The Results
After 6 months, final results indicated that both intervention groups lost an equal percentage of body weight (~10%) and had similar reductions in fat mass (25%). However, only the exercising group experienced significant improvements (vs. baseline) in cardiometabolic risk factors such as diastolic blood pressure, insulin sensitivity and LDL cholesterol (see Table 1). The authors of the study concluded:
“Our results strongly suggest that inclusion of regular aerobic exercise (or training) in a weight loss program yields cardiometabolic health benefits beyond those of weight loss alone.”
Table 1. Changes in cardiometabolic risk factors after 6 months of caloric restriction or caloric restriction + exercise. (*) represents a statistically significant difference vs. baseline measurement. As you can see, caloric restriction alone failed to significantly alter most of the metabolic risk factors vs. baseline measurements. In contrast, caloric restriction + exercise significantly improved these factors vs. baseline. DP = Diastolic Blood Pressure, Total-C = Total Cholesterol, LDL-C = LDL Cholesterol, HDL-C = HDL Cholesterol.
| Group | DBP | Total-C | LDL-C | HDL-C | Insulin Sensitivity |
| Calorie Restriction | -2% | -5% | -6% | +10% | +40% |
| Calorie Restriction + Exercise | -5%* | -9%* | -13%* | +10%* | +66%* |
What Does This Mean?
On one hand, I somewhat agree with John Cloud. Too many individuals use exercise as justification for eating high calorie, fattening foods such as doughnuts and candy bars. However, I strongly disagree with him that exercise is not beneficial. There is one fundamental equation governing body weight: Kcal intake (food) – Kcal out (resting metabolism+ PHYSICAL ACTIVITY+ thermic effect of food) = change in body weight. Regardless of how you accomplish an energy deficit (kcal out>kcal in), you’ll lose weight. As you can see from both this simple equation and the aforementioned study results, equal weight loss can be achieved both ways. A naïve reader could argue that exercise is not beneficial for losing weight, as similar body composition and weight loss changes were seen in this study. However, those exercising were able to lose the same amount of weight (as non exercisers) while eating ~ 400-550 more kcal/day. Yes, they had to exercise which took time (~45-55 minutes), but if you’re like me, and love food, I’d gladly accept this tradeoff! I commonly hear people state that they simply don’t have the time to exercise. If you find yourself in this group, simply split the exercise into multiple sessions/day such that the cumulative effect of the exercise equals 45-60 minutes. Another simple suggestion is to exercise while doing another activity (ie- ride a stationary bike while watching TV).
This study also provides strong evidence that losing weight through a combination of kcal restriction and aerobic exercise has a greater impact on improving overall health vs. kcal restriction alone. Only those exercising experienced positive cardiometabolic changes vs. baseline. In my opinion, this is pretty dang important! Reductions in LDL levels and diastolic blood pressure are both believed to be important for heart health. Increased insulin sensitivity also plays a role in cardiovascular health. For those unfamiliar with the term insulin sensitivity, it refers to how efficient one’s cells are at responding to insulin. If cells have lack insulin sensitivity (ie- insulin resistant), more insulin must be released to exert its desired effects. This occurs in type 2 diabetes which is characterized by insulin resistance. Many individuals are familiar with this role of insulin. However, far fewer realize that insulin also impacts cardiovascular health through its ability to regulate vasodilatation via nitric oxide stimulation and other related pathways3.
Insulin also plays a role in body composition. As detailed in the article, Post Workout Nutrition: Strength/Ball/Speed Athletes – Part 2 acutely elevated insulin levels are beneficial for protein synthesis. However, when insulin levels are chronically elevated (vs. strategic times of the day) one is less efficient at utilizing their fat tissue for energy, making it harder to lose those love handles4! This begs the question, “Why was there no significant difference in body composition despite one of the kcal restriction groups exercising and improving insulin sensitivity?” I can’t say with 100% certainty. Looking at the same data, Redman et al hypothesized that a true difference in body composition may have existed, but due to a smaller number of participants, it just didn’t show up as statistically significant5.
A Couple Final Application Notes
I’d like to point out one potential detail that may be forgotten when applying these results to the general public. These results were obtained using overweight individuals (25+<+BMI<30; BMI= height (m^2)/weight). Due to individuals anthropometric (wt, ht, body comp) and training intensity differences, one may have to work longer/shorter to burn an equal number of kcal/session as seen in the study. If body composition (ie- %body fat), training intensity and mode of exercise are held constant, heavier individuals burn kcal quicker than lighter individuals.
On a final note, when deciding what type of weight loss strategy works best for you, don’t forget about resistance training. Loss of lean muscle mass commonly occurs with weight loss (especially if you have lower % body fat at baseline6). However, evidence seems to indicate that adding resistance training to your weight loss program will help attenuate this loss in lean muscle tissue7.
Bottom Line
In summary, weight loss is achieved by creating a kcal deficit. This can be achieved through diet, exercise, or a combination of the two. However, it appears that significant improvements in cardiometabolic risk factors are only achieved when exercise is included as part of the weight loss program.
References
1 Cloud J. Why Exercise Won’t Make You Thin. Time. Aug. 09, 2009. Accessed on January 20, 2010 from: http://www.time.com/time/printout/0,8816,1914857,00.html.
2 Larson-Meyer DE, Redman L, Heilbronn LK, Martin CK, Ravussin E.
Caloric restriction with or without exercise: the fitness versus fatness debate. Med Sci Sports Exerc. 2010 Jan;42(1):152-9.
3 Muniyappa R, Quon MJ. Insulin action and insulin resistance in vascular endothelium. Curr Opin Clin Nutr Metab Care. 2007 Jul;10(4):523-30.
4 Zhang J, Hupfeld CJ, Taylor SS, Olefsky JM, Tsien RY. Insulin disrupts beta-adrenergic signalling to protein kinase A in adipocytes. Nature. 2005 Sep 22;437(7058):569-73.
5 Redman LM, Heilbronn LK, Martin CK, Alfonso A, Smith SR, Ravussin E; Pennington CALERIE Team. Effect of calorie restriction with or without exercise on body composition and fat distribution. J Clin Endocrinol Metab. 2007 Mar;92(3):865-72. Epub 2007 Jan 2.
6 Forbes GB. Body fat content influences the body composition response to nutrition and exercise. Ann N Y Acad Sci. 2000 May;904:359-65.
7 Stiegler P, Cunliffe A.The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss. Sports Med. 2006;36(3):239-62.
8 Image created by elisfanclub. Accessed June 14, 2010 from:http://www.flickr.com/photos/elisfanclub/318259369/