Thread by @Gonzalez_JT

De Novo Lipogenesis (DNL) is the production of fat (lipids) from other sources

E.g., conversion of sugars to fats

So what happens to DNL if calorie intake is restricted?

A 🧵that might surprise you...
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doi.org/10.1113/JP2777…
#fasting #science #nutrition #metabolism

First, a quick poll before reading on

If mice 🐁 are calorie restricted 🍽️ for a prolonged period of time (provided 30% fewer calories than they would choose to eat normally at baseline), what will happen to DNL?
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The Q is a bit vague to have a clear A, as it depends if we are talking about DNL in liver, adipose tissue, or the whole body.

Before we delve into those areas, its worth noting that mice do lose weight when restricting calories by 30%

🔗doi.org/10.1152%2Fajpe…
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When calorie restricted (CR), 🐁 can burn ~370 mg fat per day

yet they are only eating ~90 mg fat per day

& this is all whilst adapted to the diets and in energy and fat balance (i.e. fat mass is stable)

So the logical conclusion is they must be making fat too
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At a whole-body level, a respiratory exchange ratio (CO2 produced v O2 consumed) > 1 indicates net DNL.

In general, ⬇️ RER = ⬆️ fat oxidation 🔥

With calorie restriction, net DNL seems to happen early after eating, and then ⬆️ fat oxidation later on
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This seems to be almost entirely explained by increased DNL in adipose tissue

This might lead us to wonder if this happens in humans...
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DNL in humans adipose tissue (SCAT) seems to happen after eating meals within energy balance as indicated by a respiratory quotient (RQ; i.e., the RER across a tissue) >1

Whether this happens with long-term calorie restriction is less clear

🔗doi.org/10.2337/db12-1…
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In conclusion, DNL can increase with long-term calorie restriction in 🐁 and this can explain how they maintain high rates of fat oxidation in the presence of low fat intake and stable fat mass.

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