他们的意思相同。但是“吃不消”通常是口语，“受不了”在口语和书面都能用。 另外，“吃不消”源自于汉语的吴语方言，在江浙地区可以理解，在中国其他地方未必广泛使用。

其实两者可以通用，但吃不消主要是指身体上不能再坚持了，比如跑受吃不消：而受不了多指心理方面，比如你的性格我再也受不了了

吃不消：与体力相关。（吃不消 = a kind of 受不了） 受不了：包括体力相关的的、精神相关的（味觉的，视觉的，嗅觉的。。。） 举例： 1、功课太重了，我感觉吃不消。（体力不支，吃不消了） 2、他的脚臭气熏天，大家都受不了（可以说受不了他的脚气,但不能说吃不消他的脚气）

by the way, i think they are both used in an informal way in oral.

”受不了" could possibly mean ”can't stand somebody or something anymore." ie. 1. 他实在受不了妻子不停的抱怨啦！He can't stand his his wife for her endless complaints any longer. 2. 车间的噪音真让人受不了。The noise in the workshop is unbearable. “吃不消”literally suggests you are physically or mentally not able to bear something；or you have had too much to endure that may caused by fatigue). For example. 每天要熬夜到凌晨一点，我身体有点吃不消了。（My body became exhausted because I had to stay up till 1:00 am every day.）In this circumstance, "吃不消”can be replaced by "受不了”。 Moreover, "吃不消" have near-synonyms such as "禁不起' or "经不起”。 wish this could help.