This is in my understanding thoroughly disproven that strength loss on a diet stems from muscle loss. 2-4 weeks in a moderate deficit (300-500 kcals) will not cost you any muscle if protein is adequate and you’re at a reasonable BF (above 8%). But it WILL cost you pounds on the bench press.
I started my diet on January first with a 400 kcal deficit. My bench went down 10 lbs in 14 days. This is not due to muscle loss.
“Does Strength Loss Indicate Muscle Loss?
Not necessarily. It’s true that a lot of people lose some strength when they diet. But it’s rarely due to muscle loss. There are other reasons.
First, notice that the strength loss is mostly on multi-joint exercises. The bench press, military press, and squats are especially affected. This loss in “strength” doesn’t happen on isolation or machine exercises, and often doesn’t affect pulling exercises.
It’s typical to maintain or even increase strength on the tricep extension, pec deck, and dumbbell lateral raise, yet see your bench press, which requires the same muscles, go down.
Clearly, this isn’t due to muscle loss, otherwise the isolation exercises would go down too. In fact, oftentimes the free-weight bench press will go down but pressing on a chest machine will stay up or even increase.
The reason? A decrease in passive stability. That’s when non-contractile elements stabilize a joint by increasing pressure. For example, if you blow up a muscle by storing more water, glycogen, and fat, that muscle becomes inflated and “packs” the joint more. This creates pressure which makes the joint more stable. Even body fat can contribute to passive stabilization and water retention.
Why is that important? Because if a joint is less stable, the body will protect itself by inhibiting force production (not allowing you to use all of your strength potential to avoid injuries). The more stable the body feels, the more of your strength it will allow you to use.
That’s why it’s common for powerlifters to “bloat up” before a meet. They’ll eat a boatload of salty, high-carb food and drink tons of water to increase both glycogen and water retention. This increases passive stability and allows them to lift more weight.
Pressing movements are more affected because they’re more “dangerous” for the shoulder joint, which is the least stable joint in the body.
Another Factor: Beta-Adrenergic Desensitization
Another reason you can be losing strength while dieting is due to beta-adrenergic desensitization.
The beta-adrenergic receptors are the ones that interact with adrenaline. At the muscle level, beta-receptors – when activated by adrenaline – increase muscle contraction strength and speed. At the brain and nervous system level, they’ll increase coordination, drive, willpower, confidence, etc.
In other words, when your beta-adrenergic receptors respond well to adrenaline, your chance of optimal physical performance is much higher.
But if they’re not responding well to adrenaline (when they’re desensitized or downregulated) then strength and speed goes down. You also find yourself in a worse mental state.
Why’s that relevant to dieting? You desensitize the beta-adrenergic receptors by overproducing adrenaline – either bursts that are excessive, or adrenaline levels that stay high for too long.
Adrenaline is increased in large part by cortisol. Cortisol increases the conversion of noradrenaline to adrenaline.
One of the functions of cortisol is to mobilize stored energy. When you’re dieting you need to mobilize more energy, so cortisol production goes up and so does adrenaline. That’s why a lot of people have a hard time sleeping when dieting.
In that regard, dieting can lead to a decrease in physical and mental performance by making you less responsive to adrenaline. When that happens, strength will go down more across the board. But it normally takes longer to occur than the strength loss from lowered passive stability.
Another reason for a loss of strength is your mental state. If you feel small and don’t sleep as well it’ll be much harder to get amped up to lift big weights. It’s like you program yourself to believe that you’re losing muscle and getting weaker – it’s a self full-filling prophecy.”
That’s from Christian Thibaudeau. He also says if you don’t lose strength you are likely not losing any muscle. But if you are, it doesn’t mean you lose muscle. He’s right.
This is incorrect.