Why you crave tomato juice on an airplane

tomato juiceI’m writing this seated on a plane heading to San Francisco. We’ve been in the air for under an hour, and the drink cart is just starting to make its way down the aisle. As the cart rolls nearer I’m forced to decide what drink I’ll be having. Since the cups are miniscule, and the liquid is largely displaced by ice cubes if one’s not quick enough to add “no ice, please” to the order, the decision is critical.

Despite the fact that I never drink tomato juice on the ground, I’m once again craving the drink in mid air. In fact, on the very first flight I took as a kid – from Athens, Greece to Toronto back in 1991 – I distinctly remember ordering tomato juice. Now, why would a 10-year old kid crave tomato juice? And why am I now having the same craving?

It has been known for some time that there exists overlap between our senses in how we perceive the world. For instance, it is well-established that the visual appearance of food influences the perception of flavour. Ever made the error of having three things on your plate of broadly the same colour? There’s just something very unappetising about it, and the flavour never seems as rich as expected. The role of our olfactory sense in the perception of flavour is well illustrated by the blandness of most food when we have a cold and are noses are congested. Differing textures are also helpful in making food more appetising.

So what about the flight experience might be playing havoc with our perception of taste and thus our craving for certain flavours. The answer, according to some recent research, appears to be cabin noise.

In the study, Yan and Dando assessed the effect of loud audio stimulation on the perception of the five basic tastes.

A total of 48 men and women evaluated multiple standardized solutions for perception of sweet, salty, sour, bitter, and umami flavours, on a validated scale while in silence (condition A) or an environment that replicated conditions found during airplane flight and landing (condition B). Specifically, cabin noise was recreated from actual airplane cabin noise recordings, delivered to participants at 80 to 85 dB through high-definition headphones.

And what did the research reveal?

First, noise that one might experience onboard an airplane seems not to affect our perception of salty, bitter, and sour flavours.

However, exposure to loud noise caused a pronounced suppression of sweetness intensity across all concentrations measured. Ever noticed how all pop drinks taste like their diet (low or no-sugar) equivalents while in the air?

Conversely, loud noise was found to increase the perceived intensity of umami flavour, found in foods and drinks containing monosodium glutamate (MSG).

Thus, the popularity of umami-rich drinks such as tomato juice onboard airplanes may be the combined result of enhanced umami taste and dulled sweet taste.

These findings may also explain the consistently poor ratings of airplane food. Then again, the cardboard that passes for chicken on planes is likely to taste just as awful on the ground as it does at 30,000 feet.

And finally, the level of noise at restaurants may also influence the flavours perceived in the foods served. Theoretically, a loud restaurant would do well to serve umami-rich foods, but focus less on desserts and sweets.

Or you could just bring industrial-strength ear plugs with you everywhere and avoid noise affecting your meal altogether.


Reference: Kimberly S. Yan and Robin Dando. 2015.  A Crossmodal Role for Audition in Taste Perception. Journal of Experimental Psychology: Human Perception and Performance.
Advance online publication. http://dx.doi.org/10.1037/xhp0000044

Category: News, nutrition, Obesity Research, Peer Reviewed Research | 2 Comments

Juice ≠ Fruit (!!!)

orange juice

Word emerged last week that Health Canada was re-considering whether it should continue to view a serving of juice (125 ml) as being equivalent to a half cup of fresh/frozen fruit.  I think this would be a wonderful development, and I believe that my own personal experience helps to explain why.

While I was growing up, I drank a lot of juice.  Over a litre a day.  During my university days, I often bought 10 or more litres of juice in a given trip to the grocery store. Whenever my roomates poked fun at all that juice consumption (which was often), I would point to the sticker on the carton stating that it was the nutritional equivalent of eating a serving of fruit.  The calories shouldn’t count, because…. fruit.

That was then.  My thinking has changed somewhat in the intervening years.  Now, I realize that drinking a small bottle of orange juice is the equivalent of eating 6 oranges, which would strike most people as excessive.  In contrast, the amount of juice in a single orange is rather pathetic:

The amount of juice in one orange

Further, a glass of Tropicana has more calories than an identical glass of Coke or Pepsi.

Calories & Sugar in 12 ounces of Coca-Cola, Pepsi, and Tropicana

And what about smoothies?  As I’ve said in the past:

Even a freshly made fruit smoothie is still pretty refined when compared to the fruit itself. It takes a fair amount of energy and chopping (not to mention a fancy modern blender) to get a pineapple to the point that you can consume it through a straw.  You can think of a fruit smoothie as essentially a piece of blueberry pie in a glass – at least in the pie the blueberries aren’t liquefied (seriously – an original size strawberry raspberry banana smoothie at Jamba Juice has more calories and more sugar than a piece of homemade blueberry pie). Smoothies may be a lot less refined than Twinkies, but they’re not all that far from Nutella or peanut butter.

So let’s all hope that Health Canada decides to make the common sense move, and stop considering juice and fruit to be nutritionally equivalent.


Category: News | 2 Comments

Burger Loss

Today’s post comes from friend and colleague Dr Jamie Burr, and was originally posted on his own blog, available here.

Last month in PEI we “celebrated” what has become an annual ritual known as Burger Love. If you are not familiar with the concept, it is an event sponsored by various government industries and the PEI beef farmers to promote local meat consumption. Restaurants across the island prepare extravagant burgers, and after eating them (at $15/piece) the patrons rank them online so that a winner is crowned at the end of the month. Let me say upfront, that I don’t think this is a bad promotion overall – and for full disclosure I will admit that I tried a burger or two myself (usually shared with my wife) and they were quite tasty.

Like anything, however, Burger Love may best be enjoyed in moderation. Whether or not moderation was practiced is up for debate, but given that 145,527 burgers (65,068 lb of beef) were sold, at a rate of almost 5,000/day in a province of only 150,000 people, I find it hard to make that case. Compounding this effect, the Guinness record attempt for 24hr burger consumption saw 9,000 burgers consumed in this time. I’m not certain that this is something we ought to be particularly proud of – but my opinion may differ from the large majority.

As a health/performance physiologist, what jumped out at me was the size and relative caloric density of these burgers, many of which contain multiple meat paddies, and sugar/fat based glazes, sauces and toppings. Using the Dieticians of Canada “eaTracker” software (link) I calculated an average Burger Love meal to fall anywhere between 1500 to 2500 kcal ranging from the somewhat modest to more lavish creations. No big deal though- you can just exercise a little more than normal and burn it off….right?


Through the month of burger lovin, it occurred to me that the caloric math was probably not at the forefront of many diners’ minds nor did it play prominently in the decision process of where or what to eat. So, for the sake of illumination, I thought it helpful to show just how much of an impact a single burger love could have on caloric balance, and how long you would need to exercise to get back to a zero-gain. For the following calculations I have made a few assumptions to represent the “average” person, which errs on the side of conservatism. Our fictitious person is a 30yr old male, of near average height (5’11”) and weight (170lb).

At a modest pace of 3mph, it would take approximately 420min (7hrs) of continuous walking. But perhaps that’s a silly comparison, because many fit 30-somethings would have no problem “upping” the intensity. If our burger-lover were to jog at a moderate pace it would only take him 280 min (>4.5hr) or if he ran at 7mph, he could cut the time of burger loss to a mere 160 min (2.7hr). Obviously, running is not for everyone, perhaps a leisurely 3hr cycle (at 23-26km/h) is more your style. Prefer to swim? No problem, at a moderate pace you could burn off half of a burger in a mere 160 min (2.6hr).

So, does this mean you shouldn’t ever eat a hamburger? Of course not, you’ve got enjoy life and good food can certainly contribute to mental (and even physical) well-being. But understanding the idea of caloric balance (even if it’s as simple as calories in vs. calories out) might be an important consideration. But on the bright side, you’ve got a whole 11 months to burn it off before next year. Unfortunately, we might need it.

Interested in figuring out more about the energy costs of certain physical activities? Check out the American College of Sports Medicine “Compendium of Physical Activities” which can be found here in hard copy, or here as an online tool.

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30% of people with a “healthy” BMI are actually obese

scaleAlthough I’ve discussed this issue a number of times over the years, every now and then a new study comes out that provides further evidence of the limitations of body mass index (BMI) as a measure of health, or even adiposity (level of fat in the body).

Recall that BMI is the most common metric used to assess body weight status, and to identify the presence of overweight and obesity. While it is great when used in epidemiological studies across thousands of people, it’s a pretty lousy measure on an individual basis. So why does it keep being used? Its relatively easy and inexpensive to measure height and weight – hence, the measure persists in clinical practice.

In this cross-sectional study the authors assessed the BMI, body fat percentage, and cardiometabolic risk factors of 6123 (924 lean, 1637 overweight and 3562 obese classified according to BMI) Caucasian subjects (69% females) between the ages of 18 and 80 years.

What did they find?

First, 29% of subjects classified as normal weight and 80% of individuals classified as overweight according to BMI had a body fat percentage within the obese range. Thus, on an individual basis BMI tends to consistently underestimate a person’s adiposity. This data implies that there are many individuals who don’t weigh that much on an absolute scale, but a large proportion of their weight is composed of fat tissue. These are people who may look thin, but tend to be soft, with little muscle tone. In a clinical setting, these folks may easily be overlooked by their physician due to their “normal weight.”

Conversely, approximately 5% of individuals classified as overweight and 0.2% of those classified as obese by BMI actually had low levels of fat mass. These individuals would be the bodybuilders of the bunch – high absolute body weight that is composed mostly of muscle mass. This is often the line of argument used to illustrate how ineffective BMI is at measuring adiposity. And yet, as I’ve criticized before, the misclassification in this direction appears to occur only rarely. This simply suggests there are simply few body builders around. More importantly, any physician should be able to conclude that the patient in front of them with a BMI of 31 kg/m2 is not actually obese when their biceps are bigger than their waist.

Finally, when compared to individuals who were actually lean (both on BMI and body fat), those with a high levels of adiposity, regardless of their BMI (normal weight, overweight or obese BMI) had poorer cardiometabolic profiles, including elevated blood pressure, blood glucose and lipid levels, as well as markers of systemic inflammation.

So how can a physician determine whether a patient with a normal or overweight BMI is actually obese? Measuring waist circumference certainly seems to help. This one measure can help distinguish those with a low versus high adiposity despite similar BMIs.

Even better, physicians could start paying less attention to weight or adiposity altogether, and evaluate more relevant markers of a patient’s health, including metabolic factors, psychological status, mobility, etc.


Reference: Gomez-Ambrosi et al. Body mass index classification misses subjects with increased cardiometabolic risk factors related to elevated adiposity. International Journal of Obesity (2012) 36, 286–294; doi:10.1038/ijo.2011.100; published online 17 May 2011

Category: News, Obesity Research, Peer Reviewed Research | 15 Comments

The “good enough” workout

spring exerciseEver notice how much more active you are in the spring/summer? You’re not alone. Research has shown that energy expended during leisure time activity is significantly greater in the warmer months of the year – at least in areas where a distinct four seasons are experienced. In the winter, when you can’t see past the snow outside your window, you’re more likely to reach for the TV remote (and that box of cookies) than to go for a walk outside. Today, you may look at photos of yourself from last August and wonder what the heck happened over the past 8 months. Unless you’re particularly motivated and bucked the trend, you may find your current self but a pasty and pudgy version of last summer’s. For those of us living in southeast Canada, and northeast US – this winter has been particularly rough. Only the most intense of die-hards can muster the courage to go for a run when its -30 degrees Celsius.

Personally, when I haven’t been able to get a decent workout in a while, as time passes I become progressively less motivated to get back into the exercise routine. With every day of inactivity I sense as though the hurdle that I need to overcome to be active again becomes greater.

Part of the problem is that I enjoy intense workouts. When I take some time off, I know I won’t be able to bring the same level of intensity I did when I was regularly exercising for some time. And this very thought is what discourages me from getting back into it.

Alas, it is time to get moving again. But how to overcome your feeble motivation?
Continue reading »

Category: Physical Activity | 6 Comments

Will exercising during pregnancy cook the baby?

A few weeks ago Dr Zach Ferraro presented an excellent guest lecture via Google Hangout for my students on the topic of exercise during pregnancy.  Zach is no stranger to this blog, taking part in a podcast last year on the same topic.  He is also one of Canada’s leading experts on the topic, which was the focus of his PhD research at the Children’s Hospital of Eastern Ontario (where we were labmates), as well as his current research.

Zach was nice enough to allow me to record the lecture, which I’ve now posted below.  In it, he assures us that exercising while pregnant will not cook the baby, among other concerns.  If you are curious at all about exercise during pregnancy, this lecture is an excellent introduction to the topic. Enjoy!






Category: Obesity Research | Tagged | 1 Comment