We all know by now that a diet rich in fast food meals and kebab takeaways, ice cream desserts two times a day and lots of sugary, fizzy drinks is bound to get anyone of us to pile on the pounds. However, the true mystery is that sometimes, we eat the right amounts and types of foods and we exercise regularly and still we put on weight.

This is not only extremely frustrating, it's a downright killer to all the self-confidence and determination we mobilize in order to embark on a fitness and weight loss regime. The answers to the question "Why am I still gaining weight if my diet and exercise are just right?" can be very surprising. Have a look at several possibilities and see if any of them apply to your current state.

One reason for weight gain can be lack of sleep. Our bodies function at full capacity when we are well-rested and our mind is clear. "When you don't get enough sleep, your body experiences physiological stress and, biochemically, you store fat more efficiently", reveals Dr. Michelle May in an interview with WebMD. When we are tired, stress levels also increase and comfort eating - such as midnight snacking - becomes a coping mechanism.

Contrary to the popular belief that living under pressure keeps you thin, stress in itself (not necessarily as a result of poor sleeping) is yet another weight gain factor. "Stress response [...] triggers a biochemical process where our bodies go into survival mode. Our bodies store fuel, slow down metabolism, and dump out chemicals (such as cortisol, leptin, and other hormones) which are more likely to cause obesity in the abdominal region", May reveals.

Prescription drugs can also cause you to gain weight. Medication used to fight depression, mood disorders, seizures, migraines, blood pressure and diabetes can cause gradual weight creep, as well as some steroids, hormone replacement therapy, even oral contraceptives. "Every drug works a little differently to cause weight gain, from increasing appetite, altering the way fat is stored, to how insulin levels change", May says. However, a few extra pounds can actually be a low price for solving a much more serious health concern - and giving up your medication without seeking medical advice should be out of the question.

Finally, weight gain can be down to an undiagnosed medical condition, the most common of which is hypothyroidism, a deficiency of thyroid hormone which can decrease your metabolism and cause you to put on weight. "If you are feeling fatigued, lethargic, swelling, hoarse voice, intolerance to cold, sleeping too much, or headaches, you should see your doctor for an easy test to determine if you have hypothyroidism", May explains.