Effects of a low carbohydrate diet on energy expenditure during weight-loss maintenance: a randomized trial (2018)

Final paper

Effects of a low carbohydrate diet on energy expenditure during weight-loss maintenance: a randomized trial (2018)

Biological and genetic factors influence human body weight. Müller et al. (2016) say,” Weight loss and weight gain are associated with declines and increases in energy expenditure, which mainly follow changes in the metabolically active component of the body.”1 Since 1970, the United States has recorded an increased number of obesity cases due to glycemic load-food consumption. The effects on body weight result from an imbalance between energy intake and energy expenditure. For instance, When an individual’s total energy expenditure exceeds the energy intake, he/she losses weight. Besides, carbohydrates’ consumption increases the blood sugar level and insulin, which then converts glucose into fat, increasing body weight. On the other hand, reducing carbohydrate consumption results in weight loss. During weight loss maintenance, individuals’ diets play a vital role. As such, Ebbeling CB, Feldman HA, Klein GL, Wong JM, Bielak L, Steltz SK, Luoto PK, Wolfe RR, Wong WW, Ludwig DS carried out research to assess the effects of dietary compositions with varying  carbohydrate to fat ratio on the total energy expenditure. The study was titled “Effects of a low carbohydrate diet on energy expenditure during weight-loss maintenance: a randomized trial.”2The authors suggested that lowering dietary carbohydrates was essential to reduce body weight since it increases the total energy expenditure.  Despite the conclusions of this study, significant limitations related to the measurement of total energy expenditure, generalization of the findings and participants’ compliance were notable.

Biological and genetic factors, in some way, affect body weight. In this article, Ebbeling et al. (2018) show the effects of diets with a low level of carbohydrates on the total energy expenditure in maintaining a low body mass index (BMI). According to the authors, BMI is highly affected by generic factors. However, there is no explanation of why BMI is higher today compared to the past 40 years. As such, this study aimed to examine the effects of a carbohydrate diet on the total energy expenditure during weight loss. The authors conducted a randomized controlled trial at Framingham State University, Massachusetts, between August 2014 and May 2017. A total of 164 adults, whose ages were between 18 and 65 years and who had a bodyweight of less than 160 kg, participated in this survey. The subjects were assigned to low, moderate, or high carbohydrate diets. An intention-to-treat and per-protocol analysis were done using SAS software. Ebbeling et al. (2018) found that the mean weight loss in the run-in phase was 9.6 kg, while in the test phase, the mean weight loss was below 1 kg. During the intension to treat analysis, the total energy expenditure varied by diet (linear trend 52kcal/d). However, total energy expenditure decreased with an increase in carbohydrate diet according to per-protocol analysis (478kcal/d).  The energy intake of individuals assigned to a high carbohydrate diet was 139 kcal/d, moderate-175 kcal/d, and low-269 kcal/d. Although this study had enough duration for intervention, there were noticeable errors in measurements, non-compliance by participants, and the findings could not be generalized.  The authors concluded that decreasing carbohydrate diet would result in higher energy expenditure during weight-loss maintenance.

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In the article, Effects of a low carbohydrate diet on energy expenditure during weight-loss maintenance: a randomized trial, Ebbeling et al. (2018) conducted a 20-week experiment to compare the effects of diets varying in carbohydrates to fat ratio energy expenditure during weight-loss maintenance. Recent meta-analysis reports no meaningful difference in energy expenditure between low carbohydrate and low-fat diets. While this research took a long period to be conducted, it showed some limitations: measurement errors, the generalization of results, and non-compliance of the participants. According to this study, participants were selected under specified conditions. For example, all participants were expected to have a BMI greater than 25 and body weights less than 160kg. They were also expected to be adults ranging from 18 to 65 years of age. However, not all participants conformed to the rules. According to Coultas and Van (2015), non-conformity by study subjects results in unreliable findings which cannot apply to the larger population.3The researchers of this study also used the doubly labeled water method to measure participants’ energy intake. Nevertheless, this method was not suitable since the tested variables were derived from randomly picked participants to achieve the target weight loss. During this period, participants’ weight loss was randomly adjusted to maintain weight loss at 2kg. Analysis by Hall et al.(2018) indicates that doubly labeled water calculations are incommensurate with body weight and fat mass changes.3  Various comments may claim that Ebbeling et al.’s study is among the largest controlled feeding study among free-living participants and is characterized by sufficient intervention duration to avoid confounding by transient metabolic adaptations to changes in macronutrient content. However, substantial long term non-compliance by the participants and significant errors in total energy expenditure measurement by doubly label water methods proves the inability to generalize the findings. Besides, the study protocol was too long to be logistically practical or financially feasible for an inpatient setting. Further studies to evaluate the effects of glycemic load on body weight and the mechanisms related to dietary composition are necessary for determining the actual energy expenditure among obese patients.

To sum up, this research shows that reducing carbohydrate diet results in reduced body weight. However, measurement errors, non-generalizability, and participants’ non-compliance limited the reliability of the findings. Although the doubly-labeled water method was used to measure energy expenditure, the accuracy of the results was questionable since the tested variables were derived from poorly selected participants. During the recruitment of participants, the authors did not conform to the participants’ basic requirements. Hence, this study’s results could not be generalized. Based on the rise of global obese cases, determining a reliable approach to reduce weight is vital. As such, more studies should be initiated to examine the relationship between diets and weight loss. The health sector should propose the best dietary combinations to the public that provide the necessary nutrients needed in the human body and do not increase body weight. Individuals should seek nutritional knowledge from specialists to develop healthy eating hence control their weight.

References

1. Müller MJ, Enderle J, Bosy-Westphal A. Changes in energy expenditure with weight gain and weight loss in humans. Current obesity reports. 2016 Dec 1;5(4):413-23. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5097076/
2. Coultas JC, van Leeuwen EJ. Conformity: Definitions, types, and evolutionary grounding. InEvolutionary perspectives on social psychology, 2015 (pp. 189-202). Springer, Cham. Available at: https://www.researchgate.net/publication/297738036_Conformity_Definitions_Types_an d_Evolutionary_Grounding

3. Ebbeling CB, Feldman HA, Klein GL, Wong JM, Bielak L, Steltz SK, Luoto PK, Wolfe RR, Wong WW, Ludwig DS. Effects of a low carbohydrate diet on energy expenditure during weight-lossweight-loss maintenance: a randomized trial. BMJ. 2018 Nov 14;363. Available at: https://www.bmj.com/content/363/bmj.k4583

4. Hall KD, Guo J, Chen KY, Leibel RL, Reitman ML, Rosenbaum M, Smith SR, Ravussin E. Methodologic Issues in Doubly Labeled Water Measurements of Energy Expenditure During Very Low-Carbohydrate Diets. BioRxiv. 2018 Jan 1:403931. Available at: https://www.biorxiv.org/content/10.1101/403931v3.full.pdf