Weight loss, or losing weight for that matter, is one of the most important factors in fighting or even preventing disease. It also can lead to death if the person is overweight (obese) if their health is not properly monitored. However, how does weight loss affect the brain? Is it affected in any way?
Weight loss can lead to an increase in fat, protein, or body fluid. Other causes of weight loss include but aren’t limited to, viral infection, cancer, bacterial infection (like CMV or HIV), gastroenteritis, depression, gastrointestinal tract disorders, and hyperthyroidism. In fact, weight loss has been associated with several of these conditions as well. A recent study published in the May issue of the Archives of Internal Medicine reported that an increased fat intake led to an increase in depression symptoms among overweight people. The same study further reported that those who were more obese were more likely to have depression than those who were of a healthy weight.
This is a strong indication that diet and obesity may be directly related. Other studies have shown that obesity is directly linked to increases in energy expenditure. As more overweight people spend more time sedentary, their energy expenditure (the amount of energy used for movement) increases, leading to higher caloric needs. This is likely one of the reasons why more people are overweight or obese.
This study looked at the relationship between obesity and depression. The participants’ mean energy intake (food eaten daily) and their metabolic rate were measured before and after a 3-week exercise program (overweight or obese) and a change in their dietary consumption pattern was implemented. Changes in the metabolic rate significantly reduced the participants’ mean energy intake and their depression scores rose significantly. However, there was no significant change in the energy intake or in the participants’ depressive symptoms.
Another study comparing elderly Alzheimer’s patients to mentally healthy younger people found that those with greater muscle mass had greater improvement in mood than those with lesser muscle mass. This observation is noteworthy because it provides the first evidence that weight loss is not only associated with increased mood but that a change in diet can indeed improve mood. These studies provide compelling evidence that diet and exercise play a critical role in contributing to positive mental health.
Finally, another group of studies comparing depressed and non-depressed overweight or obese people found that depression was positively associated with changes in regional cerebral blood flow. This study found that greater amounts of cerebral blood flow were found in those with greater weight loss. This finding provides additional support for the notion that depression may play a significant role in the link between obesity and depression. The increased flow of cerebral blood is believed to contribute to improved mood through regulation of the stress response system. While more research is needed to completely understand the physiological underpinnings of depression and weight loss, these studies provide additional support for the hypothesis that depression and weight loss are positively associated.