You Asked: Is there any food or beverage that leads to a “negative” calorie balance?
Easy answer. No. There is nothing that can be consumed that causes a greater expenditure of calories than it provides. But advertisers have given the idea a shot. But it wasn’t long before the idea was shot down. There’s no doubt that soft drink producers are in a quandary. Their product is coming under increasing nutritional scrutiny and it is not faring well. Schools are eliminating the sales of soft drinks and the public is becoming increasingly wary of consuming sugar-laden beverages with “empty calories.” Replacing sugar with artificial sweeteners does not seem to be the answer to the marketing woes, mainly because of the common (generally unjustified) perception that these substances are mired in unresolved safety issues. So if empty calories or zero calories don’t boost sales, how about “negative calories?” A beverage that causes more calories to be “burned” than it supplies certainly sounds attractive. And back in 2006 the Coca Cola Company claimed it had come up with just such a product in “Enviga,” a green tea-based drink.
At the time Dr. Rhona Applebaum, chief scientist for Coke claimed that “Enviga increases calorie burning and represents the perfect partnership of science and nature.” Well, let’s take a look at this “perfect partnership.” First, a bit about the terminology. Calories cannot be “burned,” they are not things, they are a unit of measure. Simply stated, a food calorie is the amount of heat needed to raise the temperature of a kilogram of water by one degree Celsius. Where then does the expression “burn calories” originate? When a substance burns, it releases heat. If a piece of pie is said to contain say 300 calories, then combusting it in a closed chamber, called a calorimeter, will produce enough energy to heat 300 kg of water by one degree.
Our body can also “burn” that piece of cake, meaning that 300 calories worth of energy is released as a series of chemical reactions decompose, or “metabolize,” the cake’s fats, carbohydrates and proteins. The products of these reactions are eventually exhaled in our breath or excreted in the urine and feces, while the energy produced is used to maintain our body temperature and supply the power needed for the proper functioning of our organs and muscles. If we do not “spend” all the calories that are potentially available, there is no need for the body to completely “burn” the food components, and the remnants are stored. Weight gain ensues!
Of course, should we then engage in some activity, the stored supplies can be called upon to undergo the reactions needed to produce the required energy, and weight is lost. Obviously then, to lose weight, more calories must be expended than are provided by the ingested food. Three servings of Enviga contained only 15 calories but according to Coca Cola stimulated the body’s metabolism to produce an extra 60-100 calories per day. These calories, given off in the form of heat, are produced when stored nutrients are converted to substances that are released from the body. The implication was that drinking 3 servings of Enviga a day leads to weight loss, although the company was careful not to make that claim.
Let’s have a look look at the science behind the hype. It all started back in 1999 when researchers at the University of Geneva made an interesting observation about the inhibition of an enzyme, catechol O-methyltransferase, by catechins, compounds found in green tea. This enzyme degrades the neurotransmitter norepinephrine which stimulates fat oxidation and heat production (thermogenesis). If norepinephrine breakdown is curbed, the thinking went, thermogenesis should be increased, potentially leading to weight loss. This seemed to mesh with the observation that Asians in general are great green tea consumers and rarely have overweight issues. Why not then try to give volunteers green tea catechins in a dosage roughly comparable to what Asians consume, and monitor their energy expenditure?
The standard technique is to place subjects in a respiratory chamber, which basically is a completely sealed room that allows the incoming and outgoing air to be monitored for carbon dioxide and oxygen levels. The “combustion” of nutrients in the body requires oxygen and produces carbon dioxide and energy (calories). Since the amount of energy produced relative to oxygen uptake and carbon dioxide released is known, total energy expenditure over a 24 hour period can be determined. When such an experiment was carried out using ten male volunteers who were given capsules every day containing 375 mg green tea catechins, their energy expenditure was increased by about 80 calories. Not very impressive, but still, scientifically meaningful and enough to spur other studies. And it was one of these studies that Coca Cola used to promote Enviga.
This time 15 men and 16 women consumed a prototype beverage three times a day containing a total of 540 mg catechins and 300 mg caffeine, which also is known to boost metabolism. Energy expenditure went up by about 100 calories a day without any change in heart rate or blood pressure, which was comforting. Since the testing period was only three days, no weight loss was noted. This study was quite small and was never published in the scientific literature, which is sort of curious given the extent of the Enviga marketing campaign.
A double-blind Japanese study in 2005 actually did show some weight loss with green tea extract. Half of 38 employees of the Kao Corporation drank a green tea beverage laced with 690 mg of catechins every day with dinner while the others had tea laced with only 22 mg of catechins. All the men were put on a diet with 10% fewer calories than needed to maintain their weight. Over three months, the catechin consumers lost 1.1 kg more than the men who drank conventional tea. Interesting. And guess what the Kao Corporation makes? Catechin fortified green tea! In Japan the Company has even been allowed to make the label claim: “due its high content of tea catechins, this green tea is suitable for people concerned about body fat.”
Enviga’s insinuation of easy weight loss led to criticism from the scientific community as well as to fines by some state agencies and lawsuits from consumers. It wasn’t long before the product disappeared from the market. The only weight loss was to the coffers of its producer.