Systematic Review of the Impact of Exercise on Depression in Obese Adolescents

ntroduction

As much of the developed world experiences an increase in obesity, with as many as 23.8% of male adolescents and 22.6% of female adolescents experiencing being either overweight or obese,1 many unexpected issues arise such as depression.2 Research suggests that in those with obesity, depression is twice as prevalent than in those with a healthy BMI.2 Depression can cause several issues including fatigue, anxiety, apathy, agitation, and loss of concentration.3 One group particularly affected by depression is overweight and obese adolescents. Studies show that overweight and obese children are not only more likely to have depression but also suffer from a worse quality of life, behavioral problems, and struggles with self-worth.4 This systematic review will focus on the question, how does reducing weight through exercise impact depression? This adds to the field by updating this area with recent articles found to the best of the author’s knowledge dating from 2004 to 2024.

Literature Review

Depression

Depression is defined as a mental disorder that can affect the way you feel, act, think, and see the world around you.5 It is known to cause feelings of hopelessness, loss of interest, and suicidal intentions.5 Depression can be caused by genetics, trauma, substance abuse, medications, and even obesity.6 Neurotransmitters can have large effects on depression with the three main neurotransmitters being associated with causing depression, they include dopamine, norepinephrine, and serotonin. Changes in the levels of any of these three can cause the onset of depression and many medications are aimed at controlling these levels in those with depression.7

The way that neurotransmitters affect depression is based on the levels of their presence and how they move between neuron synapses. Neurons have times when they absorb neurotransmitters as well as times when there is no uptake. When the neurons are at rest, they experience reuptake where the unused neurotransmitters are gathered and will then be reused.8 Depression is caused by a lack of dopamine, serotonin, and/or norepinephrine. Serotonin helps mood, sleep, digestion, blood clotting, as well as others. Norepinephrine helps to reduce stress and enhance focus. Dopamine helps to drive pleasure and reward seeking. This means that the lack of these between neurons, (i.e., synapses) is not able to improve mood and can cause depressive symptoms.8 Antidepressant medications (i.e., SSRIs and SNRIs) work by making certain neurotransmitters more available by limiting their reuptake.8

Obesity

Obesity can be defined as having excess body fat and is measured as having a body mass index of 30 or higher. BMI is calculated by taking weight in pounds divided by height in inches squared and then multiplying the results by 703. While BMI has its drawbacks such as not always accounting for differences in race, sex, and culture it is still widely accepted and serves as a standard measurement worldwide.9 Differences in sex can account for BMI issues with women having a higher body fat percentage than men and a different distribution of fat.10 Not all cultures view obesity the same, with some cultures including but not limited to some within Africa and Asia seeing obese and overweight individuals as rich, healthy, strong, and even more fertile.11 Race can also play a factor with certain genetics being more likely to be affected by obesity.12 Body fat distribution can differ based on race leading to BMI creating differences in who is considered overweight and obese, this creates a racial divide in those who are considered obese based on the distribution of fat.13 One study found that black and Hispanic women had a significantly higher average BMI than white women while also having a lower body fat percentage.13 Obesity can cause numerous physical health issues.14 Some possible conditions include cardiovascular disease, type 2 diabetes, sleep apnea, osteoarthritis, and even some cancers.15

Adolescent Obesity

Within the adolescent population, depression caused by obesity is a large problem with many obese children experiencing much lower quality of life scores especially those who are obese in the prebuttal and early stages of puberty.16 These groups also are at a higher risk of mental health issues based on their perception of their weight. Students polled in certain schools within South Korea found that children and teens who saw themselves as overweight had mental health issues including depression and stress.17 Those suffering from obesity in adolescent communities are greatly affected by mental health issues and some issues may persist long after their younger years. These health issues later in