Maintaining a calorie deficit causes weight loss, but the question is whether it causes sustainable weight loss. If you lose weight, but are constantly hungry,

Maintaining a calorie deficit causes weight loss, but the question is whether it causes sustainable weight loss. If you lose weight, but are constantly hungry, irritable, suffer from headaches and lightheadedness, will you really succeed at keeping the weight off? I'd argue that most people are more interested in sustainable weight loss (some exceptions, e.g. losing weight to fit into an outfit for a professionally photographed lifecycle event).