I remember when I went back to uni for fall semester last year, I gained 4.3 lbs; my dad (nearly 50 but still does pull-ups and push-ups for fun), started freaking out and basically had me live on rice porridge, soybean soup, kimchi, and steamed spinach and robok leaves until I lost the weight. My parents have been wearing the same pant size since they were 17. Some of my dad's clothes are 30 years old.  Damn, your parents are hardcore. I love it.