Expert Review
Conflicts of interest:
None
Take Home Message:
- Leptin resistance and obesity are closely linked.
- For individuals who are obese, undertaking a minimum of 180 minutes of moderate exercise per week may help improve leptin levels.
- However, this may only be one step in the management of obesity.
- Individuals who are obese should always consult a healthcare professional before undertaking any exercise programmes.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction
- Leptin is a peptide hormone produced in the adipose tissue that is responsible for the regulation of appetite, neuroendocrine function, and energy homeostasis.
- High levels of leptin have been associated with poorer health outcomes such as obesity and people with obesity may struggle to decrease their leptin levels due to the occurrence of a state of leptin resistance.
- Exercise may help to reduce leptin levels and this meta-analysis aimed to determine how the dose-response of exercise influences plasma leptin levels during training and/or after training.
Methods
- This was a systematic review and meta-analysis of studies from 2005 to May 2023.
- Studies included were in English, peer reviewed and performed on humans.
- Any type of exercise was included in the review.
- Studies had to evaluate Leptin concentration at rest and soon after exercise and/or after a training period.
- Studies in children and those over 60 years or in menopause were excluded.
Results
- 6471 studies were identified. 25 studies met the inclusion criteria.
- Exercise, and caloric restriction plus exercise, has an acute effect on reducing plasma leptin levels (p = 0.035, n=262 16% female and 84% male).
- Short and long term exercise, and caloric restriction plus exercise has a significant effect on reducing plasma leptin level (p<0.001, n =377 38% female and 62% male).
- Sub-analysis showed that the intensity of exercise had no differing effects on leptin levels in the short-term (high-intensity: p = 0.279; moderate-intensity; p = 0.990; maximal-intensity: p = 0.256).
- Sub-analysis showed that the consumption of a pre workout meal had overall less effect on acute leptin levels (P=0.201) than those who did not eat before had lower acute leptin levels (P=0.003).
Conclusion
- Acute and chronic exercise reduce leptin levels, however if a pre-exercise meal is consumed then short-term leptin levels showed less effect overall.
- Significant reduction in leptin levels occur when exercise is performed under fasting conditions.
- Exercise intensity has no effect on short or long-term leptin reduction if 180 minutes of moderate intensity and 120 minutes of high-intensity exercise is performed.
Clinical practice applications:
- Individuals who are overweight or obese may be experiencing leptin resistance.
- The recommendation of exercise to individuals who are obese may reduce leptin levels and aid leptin resistance especially if exercise is performed under fasting conditions.
- 120 minutes of high intensity exercise or 180 minutes of moderate intensity exercise are optimum.
- Leptin resistance is not the only factor involved in the development of obesity.
Considerations for future research:
- It would be interesting to understand if decreasing leptin levels reduce body weight and if not, what else maybe aiding fat storage.
Abstract
BACKGROUND The importance of leptin in controlling body mass has recently gained more attention. Its levels are directly associated with the amount of fat mass, but not necessarily dependent on it. Exercise has great potential in reducing leptin levels, however the response of exercise to this cytokine is still not well understood. OBJECTIVE The objective of the review was to analyze the effects of physical exercise on plasma leptin concentration, either acutely (post-exercise/training session) and/or after a training period (short- or long-term), as well as to investigate the existence of possible moderating variables. METHODS The studies included in this systematic review were published between 2005 and May 2023. Only peer-reviewed studies, available in English, performed with humans that evaluated the effects of any form of exercise on leptin levels were included. The search was conducted on May 03, 2023, in Embase (Elsevier), MEDLINE via PubMed®, and Web of Science (Core collection). The risk of bias in the included trials was assessed by the Physiotherapy Evidence Database tool, considering 11 questions regarding the methodology of each study with 10 questions being scored. The data (n, mean, and standard deviation) were extracted from included studies to perform random effects meta-analyses using standardized mean difference between the pre- and post-intervention effects. RESULTS Twenty-five studies (acute effect: 262 subjects; short- and long-term effect: 377 subjects) were included in this systematic review and meta-analysis. Short- and long-term physical exercise and caloric restriction plus exercise reduce plasma leptin levels, presenting statistically significant differences (p<0.001); as well as acute effect (p = 0.035), however the latter result was influenced by the pre-exercise meal as shown in the subgroup analysis. In this meta-analysis the effect of moderating factors on leptin reduction, not addressed by past reviews, is verified, such as the relationship with caloric restriction, exercise intensity and pre-exercise meal on acute responses. CONCLUSION Both acute and chronic exercise reduce leptin levels, yet the acute effect is dependent on the pre-exercise meal. In addition to having a long-term reduction in leptin levels, the minimum amount of weekly exercise to have a significant reduction in plasma leptin is 180 minutes of moderate-intensity exercise and 120 minutes of high-intensity exercise.
