This week my awesome gym (Bakar Fitness) was once again offering hydrostatic body fat testing courtesy of Fitness Wave.

I had my body fat and metabolic rate tested last year and thought it would be interesting and informative to go in for a one year follow up.

I also want to give you an idea of what to expect if you decide to “get dunked.”

(note: This is part 1 of a 2 part post. The first post focuses on the hydrostatic testing experience rather than my personal story. Come back next week for part 2).

“Hydrostatic” body fat testing is a lot like it sounds: you get weighed under water. The principle behind the method is that virtually all tissues in your body–bones, muscles, organs–weigh more than water. That is, everything sinks except fat. The density of fat is lower than other tissues and consequently, fat weighs less.

Using this knowledge you can calculate how much fat you have by comparing your weight inside and out of the water. The lighter you weigh under water compared to on land, the more fat you have. You can convert this into an exact body fat percentage by doing a little math. (Don’t worry, Fitness Wave does this all for you).

Calculations are even more accurate when you throw in measurements like height. For this test I even had my ankle size measured.

During the test you step into a tank of warm water (pictured to the right) and position yourself on a metal scale. You are instructed to blow out all the air from your lungs and submerge your head while the operator checks your weight. This process is repeated at least three times, and takes about five minutes.

The bottom line is that when packing your bag for your body fat test remember that you will get wet.

A bathing suit and towel are appropriate.

If it is January (or summer in San Francisco), you may also want to bring a change of warm clothes and sandals. When testing, the Fitness Wave trailer is stationed down near the loading docks between the Community Center and Genentech Hall at UCSF Mission Bay. You probably don’t want to walk from the locker room to the trailer in your bikini.

Hydrostatic Testing Checklist:

1. Bathing suit
2. Towel
3. Warm clothes
4. Convenient shoes
5. Healthy dose of perspective

Packing your bag is not all the planning you need to do before getting a body fat test. As I explained last year, I also recommend you decide before you go about what you will do with this personal information. Determine beforehand whether or not you want to tell your friends what you are made of to save yourself from stress and awkward conversations later on.

Overall the testing was (once again) a great experience, and I highly recommend getting a hydrostatic test if you get the opportunity. I received a print out of my numbers and an email with more information the next day.

Next time I will reflect upon how my eating and workout habits have affected my body composition over the last year. Check back next week for all the gossip.

Keep up with Summer Tomato by using these links to receive posts via email or RSS feed. Email subscriptions require an activation step once you receive a confirmation in your inbox.

Click here to read Body Fat Test: One Year Later (part 2)

Have you ever had your body fat tested? Are you interested?

Tags: Bakar Fitness, body fat, Fitness Wave, hydrostatic body fat test, Mission Bay

A study published last week in the journal Obesity may make you question whether you really want to rely on the Atkins or South Beach diets to reach your New Year’s Resolution goals.

It is widely believed that low-carbohydrate, high-fat diets support weight loss in most individuals and indeed, there is a good amount of research to back this claim. Despite this, few studies have examined the after effects of a low-carb diet, particularly once normal eating is resumed.

In a new study, scientists had rats consume either a regular high-carb diet or a low-carb, high-fat diet for sixteen days. After this period the diets were switched and rats were maintained on the opposite diet for another sixteen days. Both diets included the same number of calories, so the only difference between the groups was the relative percentage of macronutrients.

As you might expect, while the rats were fed a low-carb, high-fat diet they lost weight compared to rats on a regular diet. Interestingly, however, despite this loss of body weight there was little to no loss of fat, and therefore the rats that lost weight had a relatively higher body fat percentage than the rats fed a normal diet.

The low-carb rats also had lower energy expenditure (exercise and calorie burning) than rats on a normal diet, and the decrease persisted even when the animals were returned to a normal diet. This is consistent with reports of exhaustion in humans undergoing very low-carb diet regimens.

Furthermore, animals that were temporarily put on a low-carb diet regained more weight than animals that were never fed a low-carb diet. This suggests that short term exposure to a low-carb diet increases risk of weight gain compared to no dieting.

Uh oh.

According to this research it is possible that a low-carb diet may actually cause you to gain weight in the long run. How very unfortunate.

But while these results are compelling, do not go stocking up on pasta just yet. First remember that these are rats, not humans. The way scientists change the composition of a rat’s diet is by giving them different pellets of bizarre lab food with various proportions of “nutrients.” This is not the way humans eat (assuming you don’t spend too much time in GNC), nor can it ever reflect a healthy human diet. It would be great if they could put the rats on a diet of seasonal fruits and vegetables, whole grains, legumes and fatty fish, but that is not the way animal research works. This is something to keep in mind whenever you hear about nutrition studies.

Also, nutrition research using rodents rarely distinguishes between the qualities of different macronutrients. For example, did the “high-fat” diet contain mostly saturated fat, trans fat, monounsaturated fats, polyunsaturated fats or all of the above? A similar question can be asked about the quality of carbohydrates, but it is difficult to imagine high-quality carbohydrates coming in pellet form. A huge body of scientific literature suggests that the quality of different macronutrients is far more important to health and weight than relative proportions of refined macronutrients.

Protein is another question mark in this study, which the authors acknowledge. The low-carb diet they used was not high in protein like a typical Atkins style diet. However, their findings were similar to studies that did use higher protein content and their animals were fed sufficient protein to maintain normal body growth, so the effect of protein on their findings is likely to be small. Their goal was to examine the effect of extreme carbohydrate restriction, and this was accomplished.

Regardless of this study’s imperfections, the results shine an interesting light on our current understanding of how relative proportions of dietary macronutrients effect body composition, long-term body weight and metabolism.

Have you experienced weight gain after going off a low-carb diet?

UPDATE: This article is also available at Synapse.

Tags: body fat, low-carb, Obesity