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Exercise as it relates to Disease/The impact of exercise and altering dietary intake in health and fitness

This is a critical piece of the research article “Effects of a popular exercise and weight loss program on weight loss, body composition, energy expenditure and health in obese women” by Kerksick et al. 2009

What is the background for this research? The widespread and increasing condition of obesity in the US and around the world from 1990-2005 reported about 1.2B overweight people with 300M of which were obese (1,2). Investigations conducted over several decades showed the critical roles played by regular physical activity and proper energy intake in the prevention and management of the harmful health effects of diabetes, obesity and cardiovascular diseases (3-7).

Rapid reductions in energy intake were found in a study having a negative impact on the metabolic rate and revealed repercussions in the reduction of fat-free-mass (8). Several dietary intervention studies from 2004-2011 with macronutrient replacements from protein to fat in iso-caloric amounts were found to have no effects on body mass loss (9-11). Other diet studies revealed that carbohydrate replacement with protein was seen to perhaps instigate weight loss at such a significant amount (12-13), and seen improvements in body composition changes and some health markers (12,14-16). Many of these investigations examined dietary interventions, but several did not include any element of exercise (14-16 ). Studies that investigated a combination of diet with and without exercise failed to provide more regulated measures to clearly explain the influence of these dietary methods if integrated with a prolonged exercise intervention (12,13). Furthermore, it was found that there was a limited number of studies that looked at combined resistance-based exercise program and dietary intervention with a focus on carbohydrate to protein replacement (8). These findings caused drawbacks in appropriately determining the form of exercise and dietary intercessions that has the greatest potential in supporting individuals to reach weight-loss and other health-related aims (17).


Where is the research from? This study was conducted in 2009 by a reputable first author Chad Kersick PhD (18-19), alongside with his colleagues who were then doctoral, masters and undergraduate students from various US Universities. Richard Kreider (20), a PhD at Baylor University and well respected in his field, served as the corresponding author. Curves International, a private fitness company that owns Curves women-only-fitness-gym (21), funded this study. Curves specialize in circuit strength training using pneumatic-resistance machines (21) and had been operating for over 20 years to date (22).

What kind of research was this? This was a matched, prospective clinical intervention study where participants were monitored for 14 weeks.

What did the research involve? The purpose of the study was to find out the safety and effectiveness of modifying the quantity of carbohydrate and protein in low-energy diets combined with the Curves exercise program in obese women.

A total of 161 sedentary obese women were assigned to the following groups: CON - no diet+no exercise, ND – no diet+exercise, or one of 4 diet+exercise (kcals; ratio % carb:pro:fat): HED high energy, high carbohydrate, low protein (2600;55:15:30), VLCHP very low carbohydrate, high protein (1200;63:7:30), LCMP low carbohydrate, moderate protein (1200;63:7:30), HCLP high carbohydrate, low protein (1200;55:15:30). Participants in the exercise group except for CON did a supervised pneumatic resistance based, circuit training program 3 times a week for 14 weeks.

What were the basic results? In over 14 weeks, all but CON had significant decreases in waist measurements. A similar but significant decrease in body mass in VLCHP, LCHP and LPHC compared to other groups. Greatest fat lost was found in VLCHP, LCMP and HCLP groups after 14 weeks. Initial dieting caused a reduction in the relative rate of REE comparable in all groups. Remarkable improvements without differences in all exercise groups on muscular fitness were seen. Lipid panels, glucose, homeostatic model assessment for insulin resistance had favourable but non-significant mean changes, while leptin levels decreased in all groups but CON after 2 weeks which remained lower after 14 weeks. Participation in exercise was seen to have significant improvements in quality of life and body image.

What conclusions can we take from this research? The researchers of the study concluded that a combination of diet with caloric-intake restrictions and resistance-based circuit exercise program instigates a significant amount of weight loss and enhances body composition measures. Similar findings from the study of Foster-Schubert et al. 2011 were observed (24). Marked losses of body mass and improvements in body composition, cardiovascular and musculoskeletal fitness were found after regular participation in the exercise program. Weight loss occurred without decreases in resting metabolic rate and findings suggests that carbohydrate replacement with protein is a potentially effective strategy to improve body composition, reduce cardiovascular disease markers if integrated with a resistance-based circuit exercise program in sedentary obese women.

Critique and Practical Advice The 4-day dietary inventory method used was expensive and time-consuming. Although it may have provided a detailed intake data without any interviewer and recall bias, this may have caused a relatively large burden on the respondent’s literacy on average intake and macronutrient type; and high motivation requirement. The possibility of under-reporting dietary intake due to the repeated measures may have occurred. The small study size inhibited the provision of adequate ability to examine the relative differences among the diet groups as well as comparison with CON and ND group. The research team could have taken advantage of the unrestricted financial allowance by hiring trained staff to collect data using a method of observation at the household level to allow findings of actual dietary intake. This way, the burden of application of measures by the respondent may have decreased allowing for more adherence and lesser dropouts. The study claimed that all 161 recruited participants completed the study which is 100% adherence. But as seen in figure 1 of page 4 of their 17-page article, 242 participants were assigned to a group (17). It is therefore unclear which stage of the study the drop-outs/terminations occurred. Assuming that the starting study population were 242, ND group appeared to have the biggest proportion (73%) of the number of participants who completed the 14-week study (17). “Non-compliance” reason for withdrawals of respondents collected the highest proportion, 75% of all 72 drop-outs. (17). The validity of the observed results can be seen as a bias that favoured the sponsor’s interests. One can question the unrestricted financial budget (23) given by the sponsor company to conduct the study. Why would a private company fund such an amount (23), without getting anything back to support their products? True enough, to date, the said company has published on its website, a concluded result found by the Exercise and Sports Nutrition Laboratory at Texas A&M University, although, unclear as to which research the website was referring to (22). The above laboratory’s website shows all completed and ongoing Curves studies on Exercise and Health (23).

The study population aimed at obese sedentary women may be seen as being focused and purposeful work due to high rates of weight and obesity (25). Yet, it may also lead someone to think that the study was promoting an all women’s program. Lastly, the findings of this study could not warrant applicability to the general public in promoting diet and exercise or both to see effects in weight loss and the like because of its short-term duration. A long-term follow-up study should be implemented to examine the long-term impacts of diet and exercise and see other contributing factors to the successful maintenance of weight loss and other fitness and health factors. In doing so, researchers will be guided to create affluent plans and implement treatment programs of obesity in the public health.