The over-expression of oxidative stress damages cellular structures together with under-production of anti-oxidant mechanisms, leading to the development of obesity-related complications. On the other hand, weight gain causes obesity that results in the depletion of enzymatic as well as non-enzymatic antioxidants.

This is supported by the observations that the susceptibility to oxidative damage is even greater in obese subjects because of depleted antioxidant sources, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT), vitamin A, vitamin E, vitamin C, and β-carotene.

Obesity has been considered as a pivotal component in metabolic syndrome and believed to have a direct associations between oxidative stress, reduced antioxidant enzymes and and metabolic syndrome. Indeed, the oxidative stress is an early event and/or a candidate for a pivotal role in the pathology of metabolic syndrome. Moreover, because of enhanced oxidative stress in obesity, the risk of development of metabolic syndrome is even more elevated in overweight or obese people.

During weight gain and in obese people, adipose tissue is characterized by increased local and systemic production of pro-inflammatory adipocytokines, which induce the production of ROS that not only generate oxidative stress on one hand but also deplete the scavenging ability of enzymatice antioxidants. The increased oxidative stress then leads to important changes in adipose tissue that promotes a systemic low-grade inflammatory response with adverse effects throughout the body including (but not limited to) the damage of cellular structures together with under-production of anti-oxidant mechanisms, leading to the development of obesity-related several diseases.

However, antioxidant therapy, elevation of enzymatic antioxidants or supplementation of non-enzymatice antioxidants in food can prevent the weight gain and thereby obesity. For instance, use of citrous juice in diet induces wight loss in normal healthy as well as obese people.

For more detail see the given link:

Oxidative Stress in Obesity: A Critical Component in Human Diseases. Int J Mol Sci. 2015 Jan; 16(1): 378–400.

Article Oxidative Stress in Obesity: A Critical Component in Human Diseases

Effects of Intentional Weight Loss on Markers of Oxidative Stress, DNA Repair and Telomere Length - a Systematic Review. Obes Facts 2017;10:648-665.

https://www.karger.com/Article/FullText/479972

Best

Dear Dr Fouad Zeidan Hamzah,

Many studies reported that an elevation in oxidative stress process is associated with weight gain but also in multiple organ dysfunction, especially liver and kidney. Here's the links of some interesting articles:

Article Oxidative stress is associated with weight gain in recipient...

Article Obesity, Oxidative Stress, Adipose Tissue Dysfunction, and t...

Best wishes,

Sabri

Several articles and research papers reveals that weight gain or obesity is directly linked with increase in oxidative stress. Whereas, loosing weight can immediately decrease the oxidative stress markers in the body indicating a reduced cellular oxidative stress. There are several research papers, but these were quite relevant, Please find the links below:

https://www.hindawi.com/journals/jobe/2013/729515/

Article Obesity, Oxidative Stress, Adipose Tissue Dysfunction, and t...

There are more, do have a look.

Best Wishes

Sabarna

The Role of Oxidative Stress and Hormones in Controlling Obesity https://www.frontiersin.org/articles/10.3389/fendo.2019.00540/full

Excess weight is defined as secondary if it is a consequence of other diseases, such as hypothyroidism or other clearly identifiable causes. In the majority of cases it is instead primary because it is not caused by other diseases, but its development is favored by several factors that interact with each other. Obesity is known to be an important risk factor for cardiovascular disease and diabetes. Less known, but perhaps even more worrying, is the contribution this condition makes to the risk of developing certain cancers, particularly breast cancer. The excess of fat does not exclusively influence the correct and timely diagnosis of breast cancer but, by altering the tumor microenvironment, it can favor its growth, progression, response to therapies, consequently worsening the prognosis. The mechanisms underlying the cancer-obesity association are multiple and distinct for the different types of cancer. Obesity is certainly associated with a series of endocrine and metabolism alterations, in particular the metabolism of sex hormones, insulin, and Igf (insulin growth factor), adipokines (hormones produced by adipose tissue), as well as inflammation. There is strong evidence linking obesity to cancer, through the alteration of the metabolism of sex hormones and chronic inflammation. However, there is clear evidence that weight loss is able to positively influence all these mechanisms, probably by regulating the balance between cell proliferation and apoptosis. Based on the studies available to date, it can be concluded that paying attention to weight reduces the risk of developing most cancers. It seems obvious to talk about many causes at the origin of primary obesity, but still, to most of the overweight or obese subjects, only a diet is prescribed, to reduce the energy introduced every day. This approach is reductive because it must be considered that there are many risk factors of excess weight such as genetic factors, hormonal factors, a sedentary lifestyle, the environment, and eating behaviors that are often influenced by psychological aspects and not least the environment internal: the microbiota. More and more experimental evidence confirms that the microbiota affects body weight. Billions of microbes in the intestine contribute to determining the total weight of the organism, directly influencing the digestion and metabolism of the substrates introduced with the food as well as the quantity of sugars, fats, and proteins absorbed by the intestine. The future lines in the treatment of obesity seem to adopt as new strategies for weight loss, interventions on the microbiota.