| Lyle's comments: This is sort of a departure from the typical paper I talk about but I think it's very interesting and, as you'll see towards the end, does have some practical implication for dieters and folks looking to alter body composition.
After the necessary introduction, the paper first looks at changes in the patterns of beverage consumption within the US. They point out that by 2004, Americans were consuming over 135 gallons of fluids other than water or about 1.5 liter per day. Basically, Americans are drinking a lot but it isn't water; obviously it's something else.
The early part of the paper also trots out something called the Beverage Guidance Panel which, in my opinion, is about as useless as the current food pyramid. It's complicated and pointless, simply confusing people more about the issue. I'm not going to bother talking about it.
Quoting the paper, they state that "While consumption of healthful beverages is falling, consumption of the most unhealthy beverages is strong." While milk and coffee consumption are at roughly one half of their historical maximum, with tea basically unchanged, regular soft drinks are the most popular beverage; beverages sweetened with high-fructose corn syrup are consumed at a rate of over 35 gallons per year on average. The second most popular drink is beer which at least has some nutrients.
Positively, low-fat milk makes up two thirds of milk consumption with soft drink consumption trending downwards. However, this may be a false artifact due to how drinks are classified, energy drinks aren't being counted as soft drinks which is making it look like folks are drinking less soda. They aren't, they are just drinking energy drinks instead.
Looking globally, drink patterns have shown massive growth with soda products being consumed at a rate in excess of one billion drinks per day. Beer consumption has shown the greatest increase with tea showing a slight increase. Wine and milk consumption have fallen globally, presumably due to the introduction of all the drinks that have made America rich, proud and very fat (my comment, not theirs).
The next section of the paper got into what is arguably the most important issue of the paper: the simple fact that for all but the last 11,000 years, the predominant fluids consumed by humans were water and breast milk and nothing else. Now, they go out of their way to point out that milk is a complete beverage containing protein, carbohydrate, fat and water. Water is, of course water which provides no calories. This is important because numerous studies have shown that humans show poor compensation for fluid calories.
Let me explain that a bit. Compensation means that the body will adjust caloric intake at other times of the day (or days later) for a given caloric load. So say you eat a bunch of candy earlier in the day and it provides 450 calories. What you might see is that, later in the day, folks eat a few hundred calories less than they'd normally eat. The body 'compensates' for the food you ate earlier. The problem is that most liquid calories aren't compensated for well and figuring out why is of some interest to researchers.
The paper suggests that one of two possible mechanisms may be at stake here. First, we may simply lack a physiological mechanism by which to compensate for liquid calories. Second, it may be that liquids are treated essentially like water, being digested/absorbed too quickly to have any impact on food intake (normally eating food does things hormonally that tends to make you eat less later).
With that out of the way, the paper examines the majority of fluids consumed by humans from a historical perspective. I'm not going into deep detail for each or this would take pages. While interesting, this really isn't that relevant to the rest of the paper or how it impacts on things like weight, fat or body composition.
The main take home point of this paper has to do with how the body responds to different beverages. Various lines of research indicate that the intake of calorically sweetened beverages do NOT reduce the intake of solid food (the compensation issue I mentioned above). Reviewing the literature, they basically point out what I wrote above. Of some interest (especially to me since I like jelly beans) one study compared the intake of 450 kcal or jelly beans to 450 kcal of a soft drink. the jelly bean consumers actually reduced their food intake by slightly more than the 450 calories in the jelly beans (my next book: the Jelly bean diet) later in the day. The carb containing soft drink group not only failed to compensate for the drink but also increased their intake of other foods slightly. That is, not only did they get the added calories from the soft-drink, they ate more food as well; a double whammy in terms of weight gain.
Continuing on, the paper addresses the issue of why the body shows weaker compensation to some fluids; the exact reason is unknown. The propose that one mechanism is in the way that the GI tract responds to the form of the food; solutions can stimulate stronger sensory responses than solid food (e.g. sweet drinks taste sweeter than sweet foods sometimes). As well, the components which make up the beverage or food may play a role.
Obviously the sight and smell of beverages are important, we may react badly to a repugnant or bitter smelling drink and well to a good smelling drink. How drinks affect the taste buds comes next; humans can taste sweet, sour, bitter, salty and something called umami. There is also a taste bud for fatty acids.
A sickness response to a drink can cause an aversion to foods down the road. Remember when you drank something and you threw up afterwards, and how the smell of that drink would make you gag? That's what I'm talking about. The sight and smell of foods also affects hormonal response, there is something called the cephalic insulin response for example, insulin can go up when people smell or taste sweet foods, long before it hits the bloodstream.
Then comes digestion where mixing with the other components of the stomach affects many things, including digestion rate. Average digestion rate of fluids is 1 cal/minute with water digesting the most quickly (no calories). Other drinks digest at relatively slower speeds depending on the composition with fat containing beverages emptying slowest.
Moving into the intestine, more stuff happens including the release of a number of different hormones many of which are involved in appetite. I don't want to detail this as there are 15 or more that may play a role here. The pattern of release of these chemicals depends on the composition of the drink and this is where we can start to see the problem.
Carbohydrates alone stimulate the least number of appetite blunting factors, protein and fat stimulate the release of more. So you'd expect much less of a compensatory response to a drink containing protein and fat (think lowfat milk) as compared to one containing only carbohydrate (think fruit juice or a high sugar soda). Which is exactly what the studies have shown. Milk shows a nice normal compensation to intake, it might as well be liquid 'food'. Soft drinks show no compensation.
So folks living on sugary drinks are causing themselves major problems. Not only do the drinks themselves have scads of calories, the body doesn't compensate for their intake. So all of those calories essentially end up being 'added' to the normal food intake (which is just as often awful in folks who drink lots of soda).
Alcohol is weird as it's treated strangely in the body. I've mentioned in previous newsletters that alcohol intake shows a weird relationship with bodyweight. Weight often goes up with alcohol intake in men but either stays the same or goes down in women. What few direct studies exist suggest that alcohol intake does not cause compensation of food intake later on. So what explains the gender difference? Most likely, men drink in addition to eating (beer and wings) while women drink instead of eating (glass of wine for dinner). Oddly, at least one piece of research suggests that regular drinkers may be more active. It may also be that drinkers under-report their true food intake.
The paper than concludes although they don't say much I didn't mention above. Humans didn't evolve on anything but water and mother's milk with other drinks such as alcohol and soft drinks coming into common usage at a much later date. Because of this, we don't appear to have evolved good mechanisms for dealing with fluid calories.
Liquids tend to digest quickly (although fluids with protein and fat, such as milk, are much slower) and carbohydrate only drinks such as soda don't release as many of the appetite blunting peptides during digestion as whole food (or milk which is a liquid whole food). This makes the consumption of sugary drinks (fruit juice or soda) a major problem. People don't compensate for intake and end up simply adding the massive amount of calories to their diet, which is often bad to begin with.
As a final take-home comment, I'm reminded of a client I had years ago. He wanted to lose weight and one of the habits I identified in him early was the intake of multiple cans of full-sugar soda. Simply switching him to diet soda saved him something like 800-1000 calories/day, he started losing at a nice 1-2 pounds per week with no other change to his diet.
In summary, in terms of the impact of fluid calories on bodyweight, bodyfat and body composition,
1. Milk good: plenty of studies show improvements in body composition with regular dairy intake
2. Non-diet soft drinks and fruit juice bad: lots of calories, no fullness, no compensation
3. Alcohol: it's complicated....we need more research. |
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