Why Long Gamma Can Lose Money Despite Gamma Scalping
Summary
A long gamma position can profit from repeatedly adjusting its delta hedge: sell some underlying as its price rises and buy as it falls. The strategy benefits from realized price movement, while the option position typically loses value over time through theta decay. Gamma scalping therefore does not guarantee a profit; the underlying must move enough to offset that decay.
The discussion identifies two key risks. If realized volatility is below the implied volatility priced into the options, hedging gains may not cover theta; with little or no movement, theta losses remain without meaningful scalping gains. Sudden price jumps can also create hedging errors because the hedge cannot be adjusted continuously at intermediate prices. The explanation is qualitative and gives no pricing model, threshold for sufficient movement, or numerical example. It also notes that changes in implied volatility can affect a position with vega exposure, so realized movement is not the only possible source of profit or loss.
Key ideas
- A long gamma position gains from realized movement through delta hedging, buying after declines and selling after rises.
- Theta decay erodes the option's value over time and must be offset by hedging gains.
- If realized volatility is too low relative to implied volatility, gamma scalping may not cover theta losses.
- Sudden price jumps can prevent timely hedge adjustments and create hedging losses.
- Implied volatility changes may also affect a position that has vega exposure.
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Full text
# Gamma portfolio trading # Gamma portfolio trading It is being said that in a long-gamma portfolio, you follow a buy-low sell-high strategy for the underlying stock, which causes you to make profit. The Theta for this portfolio is negative. But it is also said that you can lose money, why though? ## Answer by AlRacoon (score 2) https://quant.stackexchange.com/a/38160 If you are long gamma, your delta is increasing at an increasing rate. In order to delta hedge this position, you will be selling stock as the stock price goes up and buying stock as the stock price falls. An explanation of gamma trading can be found in my response to this question: What really is Gamma scalping? If you are long gamma, you are long realized volatility. In other words, you need the underlying stock to move to make money from the gamma (although you may also be long vega, in which case you will make money if the implied volatility goes up and the stock does not). If the stock does not move, the option position will lose money every day by the theta. The theta is the premium decaying over the life of the option. ## Answer by nbbo2 (score 2) https://quant.stackexchange.com/a/38162 There are two ways you can lose money: The actual volatility of the stock is less than the IV you assumed. For example (extreme case) let's say that the stock price does not move at all: you make no money at all on the gamma scalping and you lose on your theta. The gamma scalping counterbalances the theta only if the stock moves "enough". The stock price moves suddenly (a jump, which violates the BSM continuous hedging condition). You are unable to adjust your hedge and thus you lose money to "hedging error" .(It is not easy to buy when prices are rocketing up and hard to sell when they are plunging).
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