21 Causes of Rapid Weight Gain
If you’re unsure what may be causing your weight gain, the list below should help you narrow it down. Please remember that you should consult your primary care physician with any weight gain (or sudden weight loss) concerns.
1. A Slow Thyroid
Known as hypothyroidism, an underactive thyroid is one of the most common causes of unexpected and rapid weight gain (3). The hormones excreted by the thyroid gland play a huge role in your metabolism. Without sufficient levels of thyroid hormone in the blood, the metabolism slows down and can lead to weight gain.
Even among all of the inconsistencies in the science of nutrition, there is one rule that is indisputable: if you eat more calories than you burn, you will gain weight.
This means that even if you are eating a completely clean diet, you can still gain weight if you don’t watch your portions. Never assume that a food is low-calorie just because it’s healthy – always double check the nutritional values.