The foods you eat, environmental factors such as a rise in external temperature, and increased humidity, medications you use, changes in hormonal levels, and certain underlying disorders could be responsible for causing body odor.
Let us have a look at the common causes of body odor.
The rapid multiplication of bacteria in the skin and the breakdown of sweat by bacteria resulting in the release of acids can cause unpleasant body odor. This means the more you sweat, the more likely you would have a bad body odor!
For example; people who work out in the gym for long hours are likely to sweat more due to which they often have an unpleasant body odor.
The foods you eat may sometimes cause temporary changes in your body odor. For example, an excessive intake of meat continuously for a few days may cause body odor in some people.
However, body odor linked to such food habits or changes in the diet tends to disappear spontaneously once the intake of meat is reduced or stopped.
The overall diet of a person can also affect body odor. Some research studies have revealed that males who consume a healthy diet comprising fruits and vegetables are less likely to suffer from unpleasant body odor than those whose diet comprises junk foods, especially high-fat, fried foods.
A higher intake of carbohydrates is also associated with unpleasant body odor.
Bad body odor, as well as bad breath, may also occur due to the consumption of foods, having strong flavors such as garlic, onions, spices, and radish.
The findings of these studies have suggested that making healthy changes in your diet, reducing your intake of meat and high carb, high fats foods, and replacing them with fresh fruit and veggies could provide an effective way to avoid body odor.
Mental stress and anxiety can cause you to sweat more, due to which you may develop a stronger body odor.
People, who suffer from hyperhidrosis disorder, tend to sweat uncontrollably and profusely, often for no apparent reason. Hyperhidrosis can be hereditary, passed on to a child from the mother or father.
However, in most cases, it occurs due to an underlying health condition such as diabetes or depression, and the side effects of certain medications.
One research study has linked hyperhidrosis to mental stress. The findings of this study have revealed that people who experience immense mental stress are prone to develop hyperhidrosis, which, in turn, can affect their self-esteem and confidence. 
These symptoms can further contribute to their anxiety thus creating a vicious cycle. One of the best ways to break this cycle is to adopt strategies to relieve stress and anxiety.
The sharp rise in the blood sugar levels in patients with diabetes may lead to a complication called diabetic ketoacidosis. Diabetic ketoacidosis occurs due to the build-up of ketones in the body to a dangerous level.
The accumulation of ketone bodies could lead to a characteristic fruity body odor and breath.
One of the best ways to avoid body odor caused due to diabetic ketoacidosis is to monitor your blood sugar levels on a regular basis and follow appropriate treatment and dietary habits to achieve optimum glycemic control.
Research studies have found that women tend to have a unique body odor that is perceived to be attractive to men during the fertile window of their menstrual cycle. 
The change in the body odor during the fertile period could be attributed to the hormonal changes occurring during this phase. It should be noted that the smell may not necessarily be pleasant or unpleasant; but just different.
Skin and vaginal infections
Infections in the skin and vagina may cause unpleasant body odor. Fungal infections affecting these tissues are typically accompanied by redness, itching, and burning.
Some common skin infections that are known to cause bad body odor include:
- Trichomycosis axillaris, a type of bacterial infection affecting the hair follicles in the armpits
- A superficial bacterial skin infection called erythrasma
- A rash in a skinfold called intertrigo that often becomes odorous in the presence of a secondary superimposed infection like candidiasis (fungal infection)
Athlete’s foot can be the cause of sudden bad odor coming from the feet. Bad odor caused due to athlete’s foot is often accompanied by itching, redness, and rashes.
It is more common in patients with uncontrolled diabetes.
Practicing healthy foot hygiene habits, wearing clean and dry footwear, and monitoring your blood sugar levels are effective ways to prevent body odor caused due to athlete’s foot.
It is surprising to note that advanced cancer could be one of the possible causes of unpleasant body odor. It typically occurs due to an infected wound in the tissues affected by cancerous changes. 
Vitamin and mineral deficiencies
Vitamin and mineral deficiencies caused due to an inadequate diet or malabsorption syndrome can sometimes cause body odor. Deficiencies of vitamin C and zinc are the common causes of increased secretion of sweat that smells foul or putrid.
- Jan Havlicek, Pavlina Lenochova, The Effect of Meat Consumption on Body Odor Attractiveness, 2006 October, Pages 747–752, doi.org/10.1093/chemse/bjl017
- Andrea Zuniga, Richard J.Stevenson, Mehmut K.Mahmut, Ian D.Stephen, Diet quality and the attractiveness of male body odor, 2017 January, Pages 136-143, doi.org/10.1016/j.evolhumbehav.2016.08.002
- Agnieszka Sorokowska, Piotr Sorokowski, and Jan Havlíček, Body Odor Based Personality Judgments: The Effect of Fragranced Cosmetics, 2016 April, doi: 10.3389/fpsyg.2016.00530, PMCID: PMC4834355, PMID: 27148138
- Kelly A.Gildersleeve, Melissa R.Fales, Martie G.Haselton, Women’s evaluations of other women’s natural body odor depend on target’s fertility status, 2017 March, Pages 155-163, doi.org/10.1016/j.evolhumbehav.2016.08.003
- Mika Shirasu, Kazushige Touhara, The scent of disease: volatile organic compounds of the human body related to disease and disorder, 2011 September, The Journal of Biochemistry, Volume 150, Issue 3, Pages 257–266, doi.org/10.1093/jb/mvr090
Photo: Ketut Subiyanto