If the loss amount is adjusted to 33%, then on average over time individuals will make a net profit. A 50% win will more than compensate for a 33% loss (0.67 * 1.5 = 1.005).
import random
l = 0.33
w = 0.5
c = 100
m = 1000
p = {k: c for k in range(m)}
n = 1000
for k in range(n):
for j in range(m):
if random.choice([0,1]):
p[j] += (w * p[j])
else:
p[j] -= (l * p[j])
print(sum([p[k] for k in p]) / len(p))
print(sum(1 for k in p if p[k] > c) / len(p))
NB: This assumes you bet your entire capital each round instead of a constant bet size. In the presence of non-ergodicity you wouldn't want to do this, but that just means it's an even stronger result that most people come out ahead.
In fact 33% happens to be the maximum loss percentage this system (win rate, win percentage, bet = total capital) can tolerate while still exhibiting higher wealth for most players over time :)