The Role of Aerobic Exercise and Diet in Weight Loss

When it comes to losing weight, there is often a difference between what clients expect and what a trainer wants them to do. Many clients believe you need more exercise, whereas coaches often believe diet yields the greatest improvements. In a recent study published in PLoS ONE, researchers reviewed the literature to find the truth.


What the research says:

• Aerobic exercise alone caused significant weight loss.
• A combination of diet and exercise had best results for weight loss and related health factors.

Study Design

The research team examined past literature on the effects of diet and exercise on long-term weight loss. The studies they looked at had to be peer-reviewed. The research was also required to cover either an active weight-loss period of six months (although many were a year long) or a shorter weight-loss period with a longer follow up (most lasting two years in total).

Results

There were twenty studies total that fit the requirements noted above. Here's a summary of some of the important findings:

• Exercise and Weight Loss: The researchers found that clinically significant weight loss can be achieved through aerobic exercise alone. However, there was a greater amount of weight lost in the programs that used diet alone. Not surprisingly, diet and exercise together were the best option.

• Health Factors: One of the reviewed studies compared diet to exercise in terms of disease risk factors, and there were no apparent differences between the two plans. Similar to the weight-loss results, there was a greater magnitude of good health outcomes, such as better cholesterol scores and blood pressure, when diet and exercise were combined.

• Weight Maintenance: None of the plans resulted in great maintenance of the new bodyweight once the weight-loss period was over. When the participants stopped dieting, they couldn’t keep the weight off.

Considerations

The advice from this study is to promote diet over exercise for weight loss and to do both together for optimal results. As the researchers noted, the combination of diet and exercise has more benefit, both for weight loss and other related health effects:

The present systematic review found limited evidence to suggest better long-term weight loss and more favorable long-term changes in body composition and chronic disease risk factors when diet is combined with aerobic exercise compared with either diet or aerobic exercise alone.

 

The researchers also emphasized that there are variations for each individual. For example, if you already eat well and want to reduce fat just a little, it might actually be that more exercise, rather than fewer calories, is the way to go. If you struggle with weight maintenance, the only answer is consistency. Weight regain is a fact of life if you don’t stick to your plan.

The research team called for further studies to investigate the role of additional factors such as resistance training and supervised exercise programs.

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Don't Count Calories to Lose Weight: The Body Fat Set Point Theory

We have all been told that 3,500 calories equals a pound of fat. This idea is taught widely in schools and published in many nutrition textbooks. We know if we follow this rule, then we can lose a total of one pound per week by cutting approximately 500 calories per day. We take this as a fact and apply without ever questioning it.

 

The Research on Calories and Fat

But can anyone reading this article tell me where this research came from? I could not, so I took to PubMed. I searched for “3500 calories equals one pound of fat” and got a message telling me, “No items found.” I narrowed my search to “3500 calories and fat” and received six results, none of which were related to the research in determining this magic number.

 

 

So, why do we keep promoting unsuccessful weight loss ideals that are not even backed up by science? Most of us will use calorie counters found on the Internet to help us establish our daily caloric needs. The most popular equation is the Harris Benedict equation. This equation was established in 1918 after looking at extremely small control groups of 136 men, 103 women, and 94 newborn infants. This research is almost one hundred years old. 

 

Really? Science hasn’t made any new discoveries since then to alter this equation and help us fight the obesity epidemic?

 

The Body Fat Set Point Theory

Fortunately, there is good research out there to help us. But for some unknown reason it’s not as well known as the whole 3,500-calories-equals-a-pound-of-fat thing. What we need to look to instead is the body fat set point theory. This theory explains that we have a group of hormones that regulates appetite and body fat storage. These hormones communicate with one another and need to be in balance in order for us to achieve and maintain a healthy weight.

 

 

"All of these hormones must be doing their jobs and working in sync in order for us to achieve an optimal weight."

The important hormones are leptin, insulin, glucagon, ghrelin, and adrenaline:

 

• Leptin was discovered in 1992 and has been found to control how much body fat we store, as well as when we are satiated. 
• Insulin is our main fat storage hormone. 
• Glucagon is the opposite of insulin. It stimulates the liver to release stored glycogen and works with adrenaline to free up our stored fats to use as energy. 
• Ghrelin tells us when we are hungry. 

 

All of these hormones must be doing their jobs and working in sync in order for us to achieve an optimal weight. Other important factors include other peptides and even certain brain regions. 

 

Leptin, Ghrelin, and Insulin

Leptin may just be the ringleader of this circus, though. Leptin is primarily secreted by our fat cells, and when levels are high, then our hunger is decreased. Ghrelin was discovered almost a decade after leptin and it controls our short-term hunger response. Ghrelin is released from the stomach lining, and when levels are high, we increase our hunger response. Both of these hormones are found to be in dysregulation during obesity.

 

LEARN MORE: Leptin: The Secret Key to Getting Shredded

 

 

Insulin has been a big focus of obesity research for quite some time. It is one reason why some people swear low-carbohydrate diets are the way to go. Insulin has a direct effect on leptin. As insulin levels rise, so do leptin levels. In fact, leptin receptors have been found on the beta cells of the pancreas, where insulin is produced. The problem is we can develop resistance to these hormones and this can cause a number of issues for us. 

 

RELATED: 60 Minutes of Exercise Can Improve Insulin Resistance 25%

 

Developing Resistance to the Hunger Hormones

When we develop resistance to these hunger-controlling hormones, it is like our body is making a phone call, but we’re not picking up on the other end. As a result, our body needs to yell louder. It does this by releasing more and more of the hormones in question. 

 

Let’s look at this scenario in terms of letpin. If we develop leptin resistance, it means more fat being stored and more food being eaten. Due to the relationship with insulin, if we have leptin resistance, then we have insulin resistance, too.

 

So, we get ourselves into this mess and then decide we need to get our weight in check. We count out our calories and subtract 500 calories per day, just as we have been taught. But in response to this low-calorie eating our body causes our leptin levels to fall. This, again, will increase our eating and fat storage. 

 

 "Due to the relationship with insulin, if we have leptin resistance, then we have insulin resistance, too."

On top of that, calorie counting does not take into effect how certain foods react with these hormones. We are told to approach everything in moderation, including our eating, but does this strategy work? Highly palatable foods have been shown to blunt both leptin and ghrelin. This is why it is easy to overeat foods such as ice cream and pizza. This can cause you to take in more calories than you even realize.

 

 

 

What We Can Do to Lose Weight

So what can we do to lose weight if low-calorie eating does not work? We can eat a diet high in nutrient-rich fruits, vegetables, and quality protein, such as grass-fed meat, fish, and eggs. Making sure that protein makes up at least 30% of your daily calories can decrease caloric intake and may increase systemic leptin sensitivity. 

 

I recommend nine to twelve servings of fruits and vegetables per day. If you are attempting to lose weight, then limit your fruits to one to three servings per day. Vegetables are high in nutrients and low in calories. They are almost impossible to overeat. Just be careful how much added sugar, salt, and fat there is in your diet, as these increase the palatability of foods and can lead to overeating.

Science Finds the Best Way to Calculate Resting Energy Expenditure

Many athletes and coaches estimate their resting energy expenditure so they can better evaluate how many calories they should be consuming daily in order to gain, lose, or maintain weight based on the needs of their sport.

In a recent PLoS ONE study, researchers evaluated existing equations to determine the resting energy expenditure. They used these equations to create new and more accurate ones.

What the research says:

• Two new equations for measuring resting energy expenditure (REE) were proven 83% accurate for men and 72-76% accurate for women.
• An existing REE calculation called the Cunningham Formula was found even more accurate.

Muscle mass is more metabolically active than fat mass, so if you have an athletic build, the equations you find on the Internet might not accurately determine your energy expenditure. Athletes tend to have more muscle mass per pound of bodyweight, theoretically giving them a higher resting expenditure.

The researchers acknowledged that a further problem with some existing equations is that they rely on information not readily available to most trainees.Because of this, the research team came up with two equations.

• The first accounted for the lean mass of the athlete. If you know your fat free mass (FFM), you can use the following equation, which is simpler than the second equation used in the study. A pinch test or electron body fat test should be able to give you your FFM.

REE(kcal/d) = 22.771 x FFM(kg) + 484.264

• The second test only accounted for the athlete's weight and height. This would be a good one to use if the lean mass of the athlete wasn't known:

REE(kcal/d) = 11.936 x weight(kg) + 587.728 x height(m) – 8.129 x age + 191.027 x sex (M=1,F=0) + 29.279

Study Design

Ninety men and women who exercised regularly had their resting energy expenditures measured using indirect calorimetry. That means the researchers measured levels of oxygen consumption and exhaled gasses to determine how much energy each of the participants used at rest.

The participants weren’t elite athletes, but they were all well-trained. They averaged about nine hours of training every week across five sessions every week. So they were fit recreational athletes, being good representatives of the average active person. They were young as well, averaging about 23 years old.

The researchers then used the various popular equations to determine resting energy expenditure. They compared the results of each equation to the actual energy expenditure as measured by their lab tests to see what was the most accurate. They also attempted to come up with better equations if there was a need.

Results

The athletes’ average daily expenditure, as measured in the lab, was 1,837 calories per day for the men and the women together. The two calculations developed by the research team had about 83% accuracy with men and 72–76% accuracy with women.

When compared to the two equations the researchers came up with, one existing equation called the Cunningham Formula resulted in even greater accuracy. You will need to know your FFM for this one, but it is the simplest equation of all:

REE(kcal/d) = 22 x FFM(kg) + 500

As an example, if my lean body mass is 176lb (my bodyweight minus my fat mass), I need to first convert that to kilograms, which ends up being 80kg. So, 22 x 80kg is 1,760, to which I add 500 for a total resting energy expenditure of 2,260.

With these equations, athletes and coaches will now be in a better position to find out how much they should be eating. Since the Cunningham Formula is the most accurate, use it to determine your resting expenditure and add in your exercise to figure out roughly how many calories you burn per day. If you don’t know your lean mass, use the first equation above.