What if I ate less?


What would happen if I ate less?  Here’s a theoretical question from a reader.  I’ve been mulling it over as it is really fundamental to what I am talking about. Here’s the question:

Professor Schofield, I have a situation for you and I would love to hear how you respond.

Given three identical 100-kg individuals (assume they are a model of a human that experiences no natural desires or whims to suppress or appease) who all burn kilocalories at a rate of exactly 2500 per day. Assigning letters ‘A’, ‘B’ and ‘C’ to these individuals.
‘A’ consumes exactly 2000-kcal per day eating nothing but candy.
‘B’ consumes exactly 2000-kcal per day eating nothing but vegetables.
‘C’ consumes exactly 2000-kcal per day eating nothing but meats.
How are the bodies of ‘A’, ‘B’, and ‘C’ going to change in 60-days?

I have read many of the points made on this blog that a calorie is not a calorie and I also understand that all three of the above diets are pretty unrealistic; however, my math background wants to align myself with the law of the conservation of energy and say that they would all lose approximately the same amount of weight.

Your response is appreciated.

OK here’s what I think would happen, and there is some evidence around this, although as usual, more metabolic wards studies would confirm it.

What happens in the eating vegetables only and eating meat only feeding regimes probably depends a little on the exact composition of the meals and the insulin sensitivity of the individual.  But I would say that for both of these regimes, it is almost certain they will lose significant weight, and stay mostly healthy.  It is possible that a vegetable diet of almost exclusively starches and frequent meals, combined with someone who is highly insulin resistant, would result in constantly elevated insulin. This of course would result in some metabolic dysregulation, where energy expenditure is down regulated and insulin shunts some carbs into fat through de novo lipogenesis. I think this is unlikely to be what a vegetable only diet would look like.  It’s most likely that they will just lost weight.  They might not be that satisfied with their food, but all should be OK at least in the short term. In the longer term, B12, essential fatty acids, and amino acid deficiencies from vegetarianism should be considered.

Overall predictions for:

  1. Meat only diet – good weight loss, good energy, reasonable regulation of energy expenditure.  Need vegetables in the longer term for fiber and other micronutrients.
  2. Vegetable only diet – weight loss, although not as great as the meat only diet.  Some down regulation in energy expenditure depending on the metabolic health of the individual and the amount of starch eaten.  Not recommended long term because of lack of essential nutrients.

Now what we really want to consider is this one.  Someone eats just candy for six weeks. They are eating less than their daily energy requirements, so given you can’t defeat the first law of thermodynamics, then the weight loss should be predictable?

Not so fast I say.  I predict a few things will happen and the extent of this will depend on the metabolic health and the individual’s susceptibility to metabolic dysregulation.  This will depend on genes, age, and metabolic history.

So for the most insulin resistant person, a candy only diet will provoke constant hyperinsulinemia.  That is to say insulin, the fat storage hormone, will constantly be elevated. That means:

  • Fat burning is switched off
  • Carbs and fat are stored as fat
  • Energy expenditure is down regulated
  • Insulin probably blocks leptin, so they still feel constantly hungry

These factors can at least theoretically conspire to reduce energy expenditure and preferentially partition energy into fat. As time goes by, the sugar and fat combination in candy makes the insulin resistance and general metabolic dysfunction worse and worse.

My prediction is that it is possible to gain fat mass and therefore weight even on a calorie restricted diet because of the dysregulation that sugar provokes.

A good example of this in action is the OB OB mouse model. These are animals bred to be leptin deficient. That means they cannot send or receive a signal from the fat cells to down regulate hunger and to increase physical activity. That’s really the model which has shown us that leptin changes energy out and partitions energy into fat at the expense of other uses.

The thing is in humans, obese people become leptin resistant, which is a similar outcome to being leptin deficient.  Either way the brain can’t see leptin and down-regulate hunger and start expending not storing energy.

High insulin and the inflammatory pathways through sugar and so forth are highly implicated in leptin resistance.

In other words, I am saying that sometimes it is at least theoretically possible to eat a lot less and still get fat. The OB OB mouse eating exactly the same food as a normal leptin producing mouse gets obese, while the normal mouse stays lean. The OB OB mouse stops moving and stores a higher amount of food as fat.  When the OB OB mouse gets leptin injections it moves more and gets leaner.  The leptin injections have no effect on the lean mouse.

The solution? Stay off the junk carbs.

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