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The statistics are alarming. 

More than two-thirds of adults in America are considered to be overweight or obese, with 1 in 20 suffering from extreme obesity.

Obesity is linked to a myriad of chronic, life-threatening diseases including diabetes, cancer, and cardiovascular disease.

It is also expensive; the estimated annual medical cost of obesity in the US is over $147 billion.

Our ‘obesity problem’ is nothing short of an epidemic.

But to solve this crisis, we first need to know what has caused it.

Which is precisely why we are here today.

To answer one simple question: what makes us overweight?

Is It Carbs or Is It Fats?

The biggest controversy that swirls around obesity is this…

Are we overweight because we eat too many carbs or too many fats?

The ‘low carb’ camp says that the best way to eliminate obesity is to cut out carbs and sugar. They maintain two premises:

  • Low-fat diets have not worked. Even though the US Department of Agriculture (USDA) Dietary Guidelines have recommended a low-fat diet for decades, the obesity problem keeps getting worse.
  • Carbs increase glucose (and insulin) levels, which in turn makes us overweight. If we lower our carbohydrates intake, we decrease our glucose levels as well as our fat gain.

Let’s look at each of these claims carefully.

The first statement suggests that if the low-fat approach has not worked, we must be overweight for another reason.

The low carb contingency points their finger at our excessive intake of carbs.

Are they right?

To evaluate, let’s look at our daily consumption of calories and nutrients to see how our diet changed between 1970 and 2010.

For starters, we now eat almost 500 extra calories a day!

Our sugar intake has increased by only 40 calories (12 percent) although our grain consumption has soared by 42 percent. However, the grains we refer to here are mostly refined grains, stripped of their fiber and nutrients versus the nourishing intact whole grains that the USDA recommends (Remember that 90% of the carbohydrates in the Standard American Diet are refined!)

Our intake of dairy has slightly decreased (13 calories), but cheese consumption has risen 153 percent. This suggests we have swapped out milk for cheese, which is problematic since cheese is the number one source of saturated fats in the American diet and very high in sodium.

Meat intake has barely changed over this time period (Although we started at elevated levels; American consumption of meat continues to be one of the highest in the world.)

The amount of fruit and veggies in our diet remained relatively unchanged, which means we continue to not eat enough of them. Only 4 percent of Americans eat the minimum 6-8 servings of fruits and vegetables every day. Our consumption of beans (which falls in this category) is particularly low.

Which brings us to fats—the part of our diet that has changed the most. Between 1970 and 2010, our fat intake increased 67 percent!

Another way of looking at this is that almost half of those extra 500 calories we eat each day come from fat (while another 37 percent comes from refined (not whole) grains).

That is a lot of fat.

So while the Dietary Guidelines might have recommended Americans consume less fat, we clearly did not listen.

These numbers tell a clear story.

Our obesity problem is caused primarily by an overconsumption of fats and oils and, to a lesser extent, refined, processed carbohydrates.

What About Glucose?

The second low-carb argument centers on glucose.

The ‘eating too many carbs makes you overweight’ logic goes like this…

  • An excess ingestion of carbohydrates spikes glucose levels in the bloodstream.
  • In turn, elevated glucose increases insulin levels.
  • Raised insulin then triggers an increase in fat storage.

According to this interpretation, the only way to ‘fix’ the situation is to eat a low-carb diet; by eating fewer carbs, your glucose and insulin levels will be lower, and you will not gain weight (fat).

This ‘low carb’ line of reasoning is flawed because it assumes incorrectly that only carbohydrates elevate insulin when, in fact, high protein and high fat foods or their addition to carbohydrate-rich meals will raise insulin as well (without an increase in blood glucose levels).

In other words, insulin response is not always proportional to blood glucose levels or to the carbohydrate content of a meal.

If you eat a diet high in fat (and low in carbohydrates), insulin may ‘instruct’ your body to burn fat instead of carbohydrates. However, it will not dip into your fat stores any more (or any less) than if your diet is based on carbohydrates.

As long as the calories consumed are close to or in excess of what you need, fat storage will remain the same.

Why Moving More Is Not the Answer

Is exercise the villain behind our obesity woes?

Many like to contend that our sedentary lifestyles are responsible for our obesity problem.

While being a couch potato definitely does not help, it is still only a tiny piece of the puzzle.

What you eat counts much more than the hours you devote to the gym.

Just to put this into perspective…

The average American eats the equivalent of a Big Mac in extra calories every day.

To work that off with exercise, you would have to walk more than two hours a day, seven days a week!

While exercise is beneficial for your overall health, remember that you lose weight in the kitchen!

And Another Vicious Cycle

Obesity is the result of a disproportionately high energy intake compared to energy expenditure.

But it is not just about consuming excess calories.

It is about what we eat and how it changes our body’s physiological responses over time.

A high-calorie, high saturated fat diet profoundly alters how the brain regulates energy balance and ultimately leads to both metabolic dysfunction and weight gain.

Even worse, the body defends these changes fiercely, which makes any subsequent weight loss through energy (calorie) restriction very difficult to maintain.

As we saw in our article about diabetes and fat, excess saturated fat causes insulin resistance, which is a hallmark of prediabetes and type 2 diabetes as well as obesity.

This is because insulin resistance leads to leptin resistance.

And it is leptin that ‘tells’ the brain when we have had enough to eat. When leptin resistance occurs, our brain does not recognize we are full.

So we eat more and more.

And our weight keeps going up.

The vicious circle is complete.

In conclusion, the obesity epidemic is linked to too much fat in the diet.

Specifically, too much saturated fat and (to a lesser extent) refined carbohydrates.

The ensuing metabolic changes (i.e. insulin and leptin resistance) caused by this excessive consumption compromises our brain’s ability to regulate appetite and satiety.

The best way out is to reduce the consumption of fats (especially saturated fats found in animal-based foods and plant-based tropical fats and oils) and revert to a low-fat, whole food, plant-based diet.

This will stop the downward spiral by replacing your previous energy-dense diet with one naturally low in calories and yet high in nutritional density.  Equally, it will ensure that the carbohydrates you eat are the right kind (i.e. ‘intact’ and unprocessed).

Obesity may be a daunting enemy but through the proper diet (lifestyle), it can indeed be conquered.

Rosane Oliveira, DVM, PhD

President & CEO, Plant-Based Life Foundation | Dr. Rosane Oliveira combines a lifelong passion for nutrition with 25 years of genetics research to create programs that help people develop healthy habits on their journey towards a more plant-based lifestyle. She is a Visiting Clinical Professor in Public Health Sciences and was the founding director of the first Integrative Medicine program at the UC Davis School of Medicine. She completed her postgraduate studies in Brazil and did her postdoctoral training in immunogenetics and functional genomics at the University of Illinois at Urbana-Champaign.