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Causes of Unexplained Weight Gain

author image August McLaughlin
August McLaughlin is a certified nutritionist and health writer with more than nine years of professional experience. Her work has been featured in various magazines such as "Healthy Aging," "CitySmart," "IAmThatGirl" and "ULM." She holds specializations in eating disorders, healthy weight management and sports nutrition. She is currently completing her second cookbook and Weight Limit—a series of body image/nutrition-related PSAs.
Causes of Unexplained Weight Gain
Physical inactivity is a significant cause of weight gain.

Weight gain can indicate a variety of illnesses, conditions and lifestyle changes. If you've experienced recent or gradual weight gain and are unsure as to the cause, seek guidance from a qualified medical professional. If your weight gain symptoms are sudden or severe, immediate medical attention may be required.

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Underactive Thyroid

Unexplained weight gain may be a symptom of an underactive thyroid, a condition known as hypothyroidism. According to the American Thyroid Association, individuals who have severe hypothyroidism are likely to gain the most amount of weight due to the condition. When the thyroid gland is under-active, important hormones are not produced, often resulting in weight gain, lethargy, puffy face and sensitivity to cold. Once hypothyroidism is treated, weight loss may occur. However, since the condition is gradual and can develop over a number of years, weight loss may also take time. If you suspect under-active thyroid as a potential cause for weight gain or other symptoms, seek proper testing and guidance from your doctor.

Physical Inactivity

Just as regular physical activity can promote healthy weight management and improve overall health, physical inactivity can do the opposite. According to the Mayo Clinic, much of the weight gain attributed to growing older and to age-related conditions such as menopause is actually due to reduced frequency and intensity of exercise. Since weight tends to accumulate while activity decreases over time, you may fail to recognize inactivity as the primary cause.

The 2008 Physical Activity Guidelines for Americans suggests 2 1/2 hours of moderate-intensity exercise or 75 minutes of vigorous, high-intensity exercise per week for adults, unless physical illnesses or conditions deter them from such activity. If you've gained weight recently and have reduced your physical exertion, lack of activity may be the culprit. Increase gradually the amount of physical activity you partake in and aim for a healthy, balanced diet for added nutritional and wellness benefits. Since weight gain can indicate a variety of conditions, seek a doctor's guidance prior to such lifestyle changes.

Pulmonary Edema and Congestive Heart Failure

Pulmonary edema, or abnormal swelling and water retention in response to heart problems, is a severe potential cause of weight gain. According to the Mayo Clinic, rapid weight gain that results from pulmonary edema may indicate congestive heart failure, a serious condition in which the heart pumps too little blood throughout the body. This type of weight gain generally appears and accumulates around the legs. If you experience severe, sudden weight gain or swelling, seek medical attention immediately as these scenarios are serious and potentially life-threatening.

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