To be fair, I have to mention that exercise alone doesn't usually lead to long-term weight loss, particularly when you have a significant number of pounds to peel off. You really need to consider your diet, too. Exercise alone won’t lead to your shedding major pounds if you have poor eating habits. Remember, it comes down to calories ("spending" more of them and eating less of them!). It's a combination of a healthy diet and exercise that will result in a significant enough caloric deficit to lead to the kind of success you want.
The Bottom Line
The truth is, there is no magic number when it comes to how much is enough exercise. Each person's calorie needs, activity level, metabolism and exercise abilities are difference. Just like no fantastic pill will ever exist to get us to our weight goals and no diet will make losing weight effortless, there isn't a guarantee that if you exercise a certain number of minutes you will meet and stay at your goal weight, but it's sure worth a try.
I have to say that your friend's idea isn't fair: In the long run, all exercise "counts" and you need to always remember that. (Any exercise is better than being a full-time couch potato!) Don't hold yourself to impossible goals or beat yourself up for not meeting someone else's idea of what is good enough. Find what works for you. If you stick to it, you will see a little bit of change really can go a long way.
