Research roundup: high-Intensity Interval Training

CW: mention of body size, appetite and weight loss in studies

Two recent studies have come out touting the benefits of HIIT, or high-intensity interval training, for women. One of them sounds great to me. The other, well, I’m not so sure about.

The first study– a nine-month community-based exercise program for lower-income older women in Brazil— showed several benefits to cardiovascular health for the participants. Here’s how it worked, according to this article from Agencia FAPESP:

The volunteers performed the exercise programs twice a week for nine months at four neighborhood community centers run by an NGO. Clinical status, anthropometric [waist circumference] measurements and specific health parameters (cardiovascular, functional, mobility etc.) were assessed before the first session (baseline), at the end of the nine-month intervention, and three months after that. 

HIIT combined with RT [resistance training] and moderate-intensity aerobic training combined with RT were equally efficacious in terms of reducing waist circumference (by 3.3 cm on average). This benefit persisted after the end of the training period. However, only HIIT combined with RT effectively lowered systolic blood pressure (7.9 mmHg) and reduced arterial stiffness (0.69 m/s), which remained so three months after the end of the training period. 

So, the big differences between HIIT and moderate-intensity training were the reduced blood pressure and arterial stiffness that they saw in the experimental group, both of them factors for lowered risk of cardiovascular disease.

But, is going hard okay for older people? Yes, say the researchers.

Previous studies by his group showed that HIIT has no risks for people with high blood pressure, obesity or diabetes, or indeed for clinical populations in general. “The protocol requires a prior assessment to confirm the absence of contraindications, such as a high risk of heart attack, for example. Generally speaking, it’s very safe,” Ciolac stressed.

Great!

Now to the second study, which measured the effects of HIIT (vs. moderate exercise and a control) on levels of ghrelin, a hormone that affects hunger. Eight males (average age 43) and six females (average age 32) underwent bouts of HIIT and moderate exercise after fasting overnight. Details below:

“We found that high-intensity exercise suppressed ghrelin levels more than moderate-intensity exercise,” explained lead author Kara Anderson, Ph.D., from the University of Virginia and the University of Virginia Health System in Charlottesville, Virginia. “In addition, we found that individuals felt ‘less hungry’ after high-intensity exercise compared to moderate-intensity exercise.”

Female [participants] had higher levels of total ghrelin at baseline compared with males, the study noted. However, only females demonstrated “significantly reduced AG”[a form of ghrelin] following the intense exercise, according to the findings.

What’s the upshot of those results? Well, here’s what one of the researchers says:

“Exercise should be thought of as a ‘drug,’ where the ‘dose’ should be customized based on an individual’s personal goals,” Anderson said. “Our research suggests that high-intensity exercise may be important for appetite suppression, which can be particularly useful as part of a weight loss program.”

Hmmm. I’m not so sure about that. Here are some reasons why:

• The study was teeny-weeny: 14 people in total
• The study measured hunger but not how much subjects actually ate after workouts (they didn’t provide meals either before or after exercising)
• The BMI of the participants was similar (avg 22), but not necessarily the fitness levels, which could explain some differential effects
• The study didn’t track weight over time– it wasn’t designed to– so we don’t know if their results would translate into weight loss
• Why are we worrying about weight loss effects with HIIT? Isn’t it good enough that HIIT may be great for us in lots of other ways? Hmmmphf.

In case I was unclear above, here’s the thing: HIIT seems like a good option for exercise for lots of people in terms of cardiovascular benefits. Lots of studies are finding benefits for different age, body weight, and other demographic groups. Yay!

]And while it may be interesting and, in some contexts, useful to note the short-term hunger-suppressing patterns of HIIT on particular groups, that is not a reason to say it is a “drug” whose “dosage” can be used for weight-loss. In part because we know that exercise (of all types) provides loads and loads of benefits– physical, psychological, social, etc.- but doesn’t affect weight loss very much. Fine with me.

So, go big, go small, go around the block (with friends, dogs, kids, groceries), and rest sometimes, too. It’s all good for us.