Obesity and Food Palatability

Great talk by Steven Guyenet on the hypothesis that increased food palatability is an important factor in growing rates of obesity.

There is no doubt that increased calorie consumption is a proximate cause of increased levels of obesity. But that is not very useful information. The question is WHY are we eating so much more?

Guyenet provides details from a number of studies which suggest that food palatability is driving our consumption of calorie dense processed foods.

  • Study found that rats ignored their rat show in favor of human “cafeteria” junk food diet and gained weight rapidly. Such tasty human food far exceeded any other rat chow diets in producing weight gains – Sclafani & Springer, 1976
  • Overweight patients who were free to consume as many calories as they wanted from a bland diet consistently lost weight without reporting hunger despite, at times, consuming less than 300 calories per day. Lean patients on the same diet maintained their body weight. “This machine-feeding regimen was nearly as close as one can get to a diet with no rewarding properties whatsoever.” – New York Academy of Sciences, 1965
  • These findings were replicated in a similar study in which “subjects reduced their calorie intake voluntarily and were always in good spirits” while consuming a bland diet. – Michel Cabanac, 1976

Guyenet has more detailed write-ups on these studies here.

Factors involved in the reward value of a diet:

  • calorie density
  • fat
  • starch
  • sugar
  • absense of bitterness
  • free glutamate (MSG)
  • textures (crunchy, soft, liquid(
  • variety
  • certain aromas
  • consistency of flavour

The last point is worth noting: the more we can depend on a food tasting the same, the more we are likely to crave it for the certainty of the food reward. Think McDonalds.

He went on to compare two weight-loss diet studies, one low carb and another low fat, and showed that loss was comparable regardless of the preponderance of these two macronutrients. It suggests that, perhaps, whether you remove fat or carbohydrates, the common factor is a reduction in food palatability.

He also gave examples of a two native peoples who, despite having diets with widely different macronutrient contents, were both extremely lean:

  • Kung San of Botswana: consumed mostly nuts, starchy tubers, fruit, assorted leaves, insects and, less often, large and small game. At times up to 58% of their diet came from a single food (Mongongo nuts). “Somewhat monotonous”. Overall their diet was 60% fat, 25% carbs, 15% protein.
  • The people of Tukisenta, Papua New Guinea: Sweet potato accounted for 90% of food consumed. The rest included taro, sugarcane, pandanus, insects and, rarely during festivals, pork. Overall their diet was 95% carbs, 2% fat, 3% protein.

It seems that the low fat versus low carb wars may be a red herring.

So what has happened to our own tribe? Americans have changed where they eat, and therefor what they eat, quite significantly over the past 100 years with the presence of fast food really taking off since the late 60’s.

Guyenet points out that this graph understates the magnitude of the change in diet as much of the food now being consumed at home is also processed.

His next graph illustrated the massive increase in sugar consumption, another marker of this processed food intake:

A similar trend is seen in the consumption of fresh versus processed potatoes:

So what’s the bottom line? Return to simple food.

“Food that is professionally engineered to maximize palatability and reward value is uniquely fattening. The solution is to avoid it.”

The first step is to eliminate comfort aka “maximum reward” foods:

  • Candy
  • Chocolate
  • Ice cream
  • Potato/corn chips
  • Cookies/cakes
  • Fast food
  • Pizza

If that thought is painful, he proposes a strategy for easing into a healthier diet. Each step requires increased effort so get comfortable with a stage before moving on to the next one:

  1. Eat three of fewer meals per day, but no snacks
  2. Cook food at home from simple ingredients
  3. Restrict palatability/reward factors that were absent in the ancestral environment
  4. Eat a few staple foods consistently, with no flavorings added

This sounds quite daunting but he claims that simple food becomes more satisfying after a 1-2 week period of withdrawal. He doesn’t actually say withdrawal but as you look at this list, you can feel the monkey on your back and he does NOT want off.

It’s a sensible plan. Should definitely work. Requires effort.
Isn’t there a pill I can take instead???

My thoughts:

What I find interesting about his theory is how it somewhat overlaps but clashes with Seth Robert’s theory behind the Shangri-La diet. The diet involves taking a small serving of flavorless calories 1-2 times per day and that this on its own seems to cause the body to change its body fat set point. Food palatability IS a factor but you don’t have to completely eliminate modern foods from your diet. Roberts does not know how this works or what the mechanism is but many people claim to have successfully lost weight this way without any other changes to their diet or activity levels.

Is it possible that Guyenet is describing a much more arduous route to reach the same Shangri-La brain hack so to speak? The question is to what extent those people who claimed to have lost weight on the Shangri-La diet have continued to eat junk food. Maybe they spontaneously lost interest in junk food due to this protocol. Perhaps the actual hack of Shangri-La is to change one’s preference for highly palatable foods.

Certainly the Shangri-La route seems much easier. But try downing 100 calories of light olive oil and you will certainly question whether it is healthier, regardless of how easy it goes down.

Guyenet’s advice is undoubtedly no-nonsense and will work. But it may require massive changes to how you meet and socialise over food. It is likely that most people could adjust to the dietary changes required here. But in the long run, how many can maintain the social changes eating an ancestral diet may require? I doubt there are many.

So yes there are still no shortcuts. And maybe that’s the point. We have all the answers, just not ones we like.


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