Soviet radiologists (professor V.D. Lindenbraten, 1969 year) had an interesting experience. They wanted to contain a barium meal in the stomach of a patient for a time, that is necessary to provide some x-ray researches. But it turns out that if the barium meal is cold (it was taken from a refrigerator), then it leaves the stomach very fast, and doctors were unable to setup their equipments and provide researches in time.
This fact was very interesting for radiologists. They did some extended experiments and they found, that if you drink after eating cold drinks (just like icy water or a coca-cola), then it reduces the time for digestion process from 4..5 hours to 20 minutes! This discovery was described by Vitaly Davidovich Lindenbraten in his doctoral dissertation "Information to the question about how heat have an effect on the human body", 1969 year, The Institute of Experimental Medicine USSR, Leningrad.
All this means that the cold water literally pushes out the food out of the stomach. This is the way to obesity, because this food can't sate you, and the feeling of hunger coming on very quickly. By the way, this activates abnormal fermentation in gastrointestinal tract because there is no normal digestion of food.
But this it the way that the fast food industry makes big money. Drinking after delicious food (sandwiches, hamburgers, hot-dogs) cold drinks you'll never get enough of it - you'll need come back and eat here again and again!
At the same time, the price for hot drinks (tea, coffee) is higher than for cold drinks, or cold drinks is not included in the meal and not advertised. But icy soft drinks are relatively cheap, and they are advertised everywhere using all types of media.
So here is the conclusion - do not drink any cold drinks immediately before and after meal. All the drinks must have room temperature or above.
In the stomach the proteins from eaten food is prepared for the next stage of processing and digestion. If you drink a clod drink shortly before or after meals, then the proteins couldn't be completely processed in the stomach, they couldn't be broken down into amino acids. The cold lump of food will leave the stomach very fast, and all proteins of the food will be putrefied in the intestines (unprocessed proteins at the temperature 36.6°C (97.88°F) and above would putrefy very quickly).
Thereby, if you drink a clod drink shortly before or after meals, you only will lose your money for the food and lose your health as well (you can get some forms of inflammatory bowel diseases - colitis, enteritis etc.).
There is a myth that is still very popular - do not drink water 2 hours before and after meals. How this myth was born? In the past, in villages, people drank cold water - it was quite hard to warm it. More often water was taken from wells, it was icy water (especially at winter time). In such conditions that was right do not drink water soon after or before meals. But in our days, in most cases, we drink warm drinks - tea, coffee, cocoa and so on, so this advice is obsoleted.
All said above is related to ice creams too! Do not eat ice creams or smoothies soon after meal, you'll get the same result - the lump of food will leave your stomach and proteins will be left undigested.
Source: the book "Anyone can lose weight" by Gennady Kybardyn