When people in general decide to lose weight, the first thought which usually comes to their mind is “I have to start exercising” – every fat loss related New Year’s resolution I’ve heard is “to start exercising”. I can’t count the amount of friends and family members who started running because they decided they wanted to lose fat. Can you guess how many of them have succeeded in reaching their goals with that approach? None.
Cardio and energy expenditure
People in general are pretty blind when it comes to estimating the amount of calories burned through aerobic exercise and understanding the equivalent amount of real food. This was demonstrated in a study from 2010 where eight lean men and women were instructed to run on a treadmill until they burned 200 and 300 calories divided on two occasions (1). They were then asked to estimate their expenditure and eat the corresponding amount of food from a buffet.
The subjects overestimated the calories burned by 300% and ate 200% more than they burned.
34% of the population in North America is considered obese and 59% are inactive. Obesity contributes to an estimated 120 000 preventable deaths in North America each year. Other obese related health risks include high blood pressure, dyslipidemia, type 2 diabetes, coronary artery disease, and stroke. Because of the link of obesity and physical inactivity, adults are recommended to engage in at least 150 minutes of moderate-intensity physical activity per week. But how effective is increased physical exercise as the single intervention for weight reduction?
The new study
A new study was published in August 2011 studying the effects of isolated cardio exercise on weight loss (2). This was a Meta-Analysis which basically means a pooled analysis of all research done in the subject – one of the most scientifically trusted methods to make an overview on the current research. 14 studies including a total of 1847 patients were selected for the analysis. The researchers studied the mean difference between the exercise and control group in regards to weight, BMI, body fat and fat distribution, cardiovascular risk, blood lipids, diabetes risk factors.
The results in weight loss are not impressive. For trials with a 12-16 week exercise program, mean difference ranged from 0.8 to 2.5 kg weight loss. Trials with 6 months duration showed a 1.6 – 2.5 kg weight loss. Studies with a 12 month intervention period showed no more then 1.4 – 2.0 kg weight loss. Very modest effects were seen in waist circumference in all periods studied. At 6 months, aerobic exercise resulted in small reductions in blood pressure and cholesterol.
The author’s conclusions:
An isolated, moderate-intensity aerobic exercise program is an ineffective weight loss intervention for overweight and obese populations. Aerobic exercise programs of 12 weeks to 12 months in length resulted in modest weight and waist circumference reduction. Aerobic exercise does provide modest improvements in cardiovascular risk and lipid levels and may have value as part of a combination program with diets. Patients and health care workers, however, should be aware that its value as an independent weight loss intervention for over- weight and obese populations is limited.
One possible explanation is that isolated cardio training leads to increased hunger and energy intake in people who use that as the primary intervention for fat loss – which might offset the benefits of the increased energy expenditure.
Fat loss is ALWAYS about creating a calorie deficit. It should be clear by now that cardio for fat loss will only be effective if combined with dietary restriction (eat less food). Cardio is just an effective tool you should have in your back pocket, and used in the right context it can be very effective, but use the tool the right way.
The Smart Way To Use Cardio During a Fat Loss Diet
I personally use an approach that which allows you to use aerobic training as an effective tool for long term fat loss. Observe that this method is used when fat loss is your primary goal for a client with main focus on conditioning or athletic performance. But if someone has any particular health issues, I might use a different approach.
- Tighten up your diet – restrict your calories to the point where you lose fat in the wanted pace. If your primary goal is simply fat loss and muscle maintenance include NO cardio in your fat loss plan when beginning you fat loss journey.
- Perform some heavy strength training a few times/week to maintain your muscle mass.
When your fat loss stalls (and it will) that’s when the perfect time to incorporate cardio training – that’s when those 200-300 extra calories will really make a difference! Just don’t overdo it since your recovery abilities will already be hampered because of the calorie restriction and you’ll need it for the strength sessions.
1. Willbond SM, Laviolette MA, Duval K, Doucet E. Normal weight men and women overestimate exercise energy expenditure. Journal of Sports Medicine and Physical Fitness. 2010;50(4):377-384.
2. Thorogood A, Mottillo S, Shimony A, et al. Isolated aerobic exercise and weight loss: a systematic review and meta-analysis of randomized controlled trials. The American journal of medicine. 2011;124(8):747-55.Svensk översättning på denna artikel kommer inom kort.
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