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Diets, diets, and more diets

Are you as confused by the diets fad out there as I am? Read on as I attempt to make sense of the broad categories of diet strategies.

One of the most common questions I get asked is:

How can I lose weight? 

This is a huge topic. So to begin, I’m going to try to tackle the broad categories of diets.

There’s just so many diets and diet fads out there, it’s hard to keep up. There’s the Atkins diet, the South Beach Diet, the ketogenic diet, the Zone diet, the Master Cleanser Diet, the Hubbard Purification Rundown… I could go on.  Weight loss is big business. It’s almost as if you can think of a system of eating less of this or more of that with pseudo scientific evidence for certain nutrient composition, slap on a snazzy name and BAM! You got yourself a diet! And as silly as some of these diet names sound, as difficult as the diet themselves are, we do it. We commit to eating less, or cut out this and that, or at least we try to. We do it not just for our vanity but for our health. We tend to think of our obsession with our weight as a modern day phenomenon, but that’s not entirely true.  The ancient Greek physician, Hippocrates, had a whole system for weight loss. He thought that optimal weight loss can be achieved by eating only one meal a day of fatty foods, preferably while panting during strenuous activity. He acknowledged that exercise is critical to weight loss. In fact, he recommended that people should walk naked for as long as possible six days of the week, and on the seventh day, meals should be followed by vomiting. I guess bulimia was not considered a medical condition during Hippocrates’ time. 

So how do we judge whether a diet plan works? Well, we generally report our results in terms of the rate of weight loss. I mean, how often have you said or heard someone say, “I lost this number of pounds over this amount of time”? The rate of weight loss is directly related to the difference between the amount of energy (or the calories) we take in and the amount of energy we burn. Eat less, burn more. Lose more weight. Simple enough. But this simplistic view is often what frustrates so many of us who are trying to lose weight. It’s really hard to eat less and it’s really hard to burn more. To make it worse, our bodies are evolutionarily adapted to help us survive starvation in that 1) we’re really good at storing consumed energy and 2) we’re really not good at burning our energy reserves. Just think of how many Thanksgiving dinners are stored in our love handles. Then think of how after a three mile run, we’ve only burned the equivalent of one slice of pecan pie. This evolutionary adaptation worked great for our hunter-gathering ancestors; not so much for today’s society. 

I’m not going to fixate further on how we’re kind of programmed to put on weight thanks to our human ancestor’s primordial environment.  And there’s not much we can do with things that are out of our control, meaning our sex, our genetic makeup, and aging. All of these factors obviously play a role in our body size and our metabolic rate. 

There are certain things that we have control over. Even though it’s hard, we can control how much we eat and what we eat. And this is the basis of all diets. All successful diets have a single mantra: eat less. Remember back to the formula? Rate of weight loss is equal to the difference between calories consumed and calories burned. Eat fewer calories. Burn more calories. How many fewer calories? Well that depends. There are many calculators available online to help you estimate your total daily calorie requirement based on your body weight and your activity level. For most adults, eating 500 kcal per day less will result in about a one pound weight loss. 

And there are loads of diet options to choose from. Broadly speaking, we can group diets into several categories. There’s the balanced low calorie diet, the low fat diet, the high protein diet, and the low carb diet.

Balanced Low Calorie Diets

Balanced low calorie diet is basically eating smaller portions of heart healthy diets like Mediterranean diet and DASH diet. For most people, this is probably the healthiest way to lose weight because in addition to weight loss, they also get the benefits of cardiovascular risk reduction and diabetes prevention.

Low Fat Diets

The other diet categories, like low fat, low carb, and high protein, take a compositional approach to dieting. This approach is based on how full we feel with certain classes of foods, how our body burns alternative energy sources when one class is lacking, and the recognition of what’s called “the thermic effect of food.” The thermic effect of food is the increase of metabolic rate observed for several hours after we eat something.  When we eat a burger, for example, the burger doesn’t magically turn into energy. We’ve got to burn energy to digest the burger, absorb it, transport it, and store it. It turns out it takes the most amount of energy to burn protein and least amount to burn fat. Carbohydrates fall somewhere in between. 

If we select for composition of food that has a higher thermic effect then maybe we can lose more weight for the same amount of total calories consumed. That’s the premise for low fat diets. Going on a low fat diet means that the daily intake of fat is less than 30% of the total energy consumed in a day. Ideally, all diet plans should keep daily intake of fat to less than 30% of total calories. That means for a 1500 calorie diet, no more than 45 grams of fat should be consumed.

High Protein Diets

High protein diets, like Paleo plans, take advantage of this thermic effect of protein. Remember, protein is the most thermogenic. The higher the portion of protein, the higher the energy expenditure. In fact, one study found that people consuming a diet containing 29% of protein had a higher resting metabolic rate than folks consuming the same calorie diet with 11% energy from protein. Thermic effect of food, and resting metabolic rate are not things we are aware of after we eat a lean piece of meat or a handful of dry nuts. But think about how we feel after eating the nuts compared to eating the same amount of say potato chips- we feel fuller, longer. So the satiety we get from a high protein diet probably helps in taking the weight off and keeping it off. 

Low Carbohydrate Diets

Low carb diets have been a very popular way to lose weight. There are two tiers of carb restriction. There’s the low carb diet like the Atkins diet where only  60 to 130 grams of carbohydrates are allowed daily. There’s also the very low fat diet, like the ketogenic diet, where no more than 60 grams of carbs are allowed daily. Low carb diets are quite effective for short term weight loss, compared for example to low fat diets. This is probably because having little to no carbohydrates in our system pushes our body to use breakdown glycogen. Glycogen is mostly water so a lot of the weight loss early on is fluid loss. So when we compared low carb vs low fat diet, the difference in weight loss between the two strategies was not obvious after a year. 

In reality, all successful diets require some sort of total calorie restriction. There are a number of diets to choose from but the key to losing weight depends on how well we can stick to the regiment. If it’s too weird or too extreme, chances are, weight loss won’t be sustainable. And since everyone is unique, you should work with your doctor and dietician to tailor your weight loss strategy. 


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