Cardio vs. weight lifting for weight loss

There are a lot of people who either claim that cardio or weight lifting is the key to losing weight. For example an article questioning the need for cardio or an article claiming that cardio is the key to weight loss.

The cardio folks usually point out the “afterburner” effect, where the body continues to burn calories even after the workout. And weight lifting people mention that muscles burn more calories than fat, so more muscle is the key.

Are there studies showing if either one is true? Or are both needed? And what about interval training?

Answer:

This is a tough question to answer as there are a lot of ifs and buts.

Weight loss is all about caloric deficit, expend more energy than you consume and you lose weight. Most people do this by dieting, but the body tends to readjust the resting metabolic rate so that you don’t lose too much reserves. Thus exercise plus diet is needed for weight loss to be effective.

How effective is ‘Diet Only’ versus ‘Diet plus Exercise’ for Weight Loss? Most studies demonstrate that when diet (caloric restriction) and physical activity are combined in a weight management program, encouraging results in weight loss occur. Donnelly and colleagues (2009) explain that a weight loss program design may create an energy deficit (e.g., 500 to 1500) composed of exercise (e.g., 250 kilocalories/day) and caloric restriction (e.g., 250 kilocalories/day) for the daily caloric deficit total (500 kilocalories in this example). In studies where investigators introduce an energy deficit of 700 to 1000 kilocalories per day, ‘diet only’ and ‘diet plus exercise’ result in similar losses. Donnelly explains that this is due to metabolic adaptations that “diminish any additive effect of energy expenditure from physical activity on weight loss”. However, in investigations where the energy deficit is 500-700 kilocalories/day, the ‘diet plus exercise’ group is about 20% greater than the ‘diet only’ intervention.

So weight loss needs to be related to your activity and diet in order to understand your basal metabolism. But weight loss isn’t just about bodyweight as it is about losing bodyfat (as muscle is useful for maintaining basal metabolism and body function). When you calculate this you are able to figure out how many calories need to be removed from the diet in order to lose fat. See here. There are also strategies that can change your metabolism.

Exercise is usually broken down into two categories: cardio and weight training. There are many benefits to both and generally both are recommended for long term health. Weight training is known to burn fat.

This study is the first to directly show that resistance exercise increases adipose tissue lipolysis and thus contributes to improved body composition. This boost in lipolysis is apparently due to the excitatory effect of resistance training on specific hormones (e.g., epinephrine, norepinephrine and growth hormone). As this study design was completed with trained male subjects, it is hoped that the methods and procedures will be completed with other subject populations (e.g., females, untrained persons, youth, seniors, overweight, etc.) in future research.

For cardio training, there is obviously fat burning taking place. The amount of fat burning that occurs is related to the intensity of the cardio.

In summary, that data clearly show that exercise intensity is the main factor in determining the magnitude and duration of EPOC following aerobic exercise. Thus, when developing a cardiorespiratory exercise prescription for weight maintenance and weight loss, the influence of exercise intensity on EPOC and its potential contribution to total caloric expenditure should be taken into consideration.

The same is true of weightlifting (from the same article):

The data on resistance training and EPOC suggest that EPOC is distinctly influenced by the intensity of the resistance training program.

The actual amount of post activity “fat burning” will be related to the intensity and duration of the exercise done. Weightlifting has advantages in terms of encouraging muscle satellite cell accumulation that sustains and grows muscle. Cardio has the benefit that it can be performed for longer durations than weightlifting. So the essential answer will come down to the individual and their strength and fitness.

Essentially any exercise program should incorporate both cardio and weight training for weight loss, especially targeting fat loss.

For more articles on fitness and metabolism see here.

Further question: Hey, do you think I can get the source on your statement that “the body tends to readjust the resting metabolic rate so that you don’t lose too much reserves.”? I’m rather curious about this. – Joel Cornett

Reply: Joel, there is a lot of research related to metabolic rate and how it changes under dieting and exercise regimes. It is quite a complex topic because it depends upon many factors. Someone who has just started dieting will be different from someone who is active already in terms of responses. Here is one paper that looks at the overweight people and weight control. I linked to Kravitz’s other articles that cover some of the athlete side of metabolism in the last link.

Do wind turbines kill many birds each year?

It has been claimed that due to their large size, and the velocity of their blades that wind turbines kill large numbers of birds that run into them at night, or in fog, and die.

http://www.wildlifeextra.com/go/news/wind-farm-birds112011.html#cr

Do wind turbines kill many birds each year?

Answer:

The simple answer is yes. The more complex answer is that the number of deaths is nothing in comparison to other man made structures and the risks from climate change.

There have been several studies done to find the environmental impact of wind farms on birds. Generally birds lack the ability to dodge humans and their quest for global supremacy. From the American Bird Conservancy there are a list of deaths related to sources as deaths per year in the US:

  • Feral and domestic cats – Hundreds of millions
  • Power lines – 130-174 million
  • Windows – 100 million to 1 billion (NB the high end seems too large to me)
  • Pesticides – 70 million
  • Cars – 60-80 million
  • Lighted communication towers – 40-50 million
  • Wind turbines – 10-40,000 (Table found here)

Obviously wind turbines aren’t as popular as cars, cats and windows, but with the expected increase in wind energy generation, the impacts will likely increase. The thing that has to be borne in mind is that the wind turbines are on an order of magnitude smaller impact than other bird killers. It also has to be remembered that the studies are also showing that newer wind power plants are having less impact on birds due to design upgrades, better placement and better ecological planning.

The real issue here is climate change. Coal power plants kill birds, in fact, they are threatening to wipe out entire species. According to a study reported in Scientific American, at least 950 entire species of terrestrial birds will be threatened with extinction as a result of climate change under several scenarios, even at the lower estimate of temperature gains, just counting species of non-sea birds in the higher latitudes; outside the tropics. Birds in the tropics will be impacted by habitat loss, which brings the total species wiped out to ~1800 (Jetz, Wilcove, and Dobson 2007).

The take home point is that we need clean energy sources to save bird species. Those that fly into turbines each year will be minimised with better designs and locations of turbines. In the meantime, worry about the cats and climate change.

Update: recent studies have shown that birds of prey are more prone to injury and death from wind turbines. Essentially, birds of prey spend a lot of time looking down for prey and not enough time looking where they are going. The usual bird collision rate is 0.08 birds per turbine per day on average (range 0.05–0.19), whilst the ‘smarter’ Eagles are colliding at a rate of 0.112 to 0.133. The study also suggests that bird size and speed of flight are important determinants of collision rates, hence why gliding and hovering prey birds are colliding more often. It is worth bearing in mind that both of these collision rates (that often result in death) still indicate an avoidance rate of 99%.

This avoidance rate is important to compare to the relative deaths per gigawatt-hour of the power sources to realise that wind power is still a very good option. This study estimates that wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour of electricity while fossil-fueled power stations are responsible for about 5.2 fatalities per gigawatt-hour. Thus, wind turbines could do with some investigation into how to make them safer for birds, but they are already a much better option than fossil fuels.

Update #2: an Australian researcher has recently done an interview on Ockham’s Razor (an ABC science show) to dispel some of the bird myths surrounding wind turbines.

Update #3: Teale commented via Facebook that the upscaling of power generation by wind hasn’t really changed the annual bird deaths per MW/hr despite the increase in the number of wind turbines and areas with wind farms. The bird deaths are ~33,000 pa, which is still in the range cited by the American Bird Conservationists from a few years ago, and the power generated has increased to ~4%. Again we come back to the point above about what other power generation and mining does to birds is a much larger impact. Remove them and the wind turbines can get a lot more prevalent and still not have the same impact. (NB: there may be some circular referencing going on between the sources in this article, so if this is the case,  please send through any revised data sources, especially on data changes with time).

http://www.fws.gov/birds/mortality-fact-sheet.pdf 

http://www.fws.gov/mountain-prairie/pressrel/11-64.html

http://en.wikipedia.org/wiki/Wind_power_in_the_United_States