Lifting heavy weights, otherwise known as resistance exercise, is not required to lose weight. You can lose weight even without doing resistance exercises. However, there are good reasons to do resistance exercises if you can, as you lose weight.
When your body loses weight, it loses a little bit of fat and muscle. This can make your muscles weaker, and leave you with less muscle tone after weight loss. Resistance exercise grows your muscles, and helps prevent this muscle and strength loss.
There are a few important things to keep in mind if you decide to add resistance exercise to your weight loss plan.
If doing resistance exercise means you do not have time to get your steps in (10,000 minimum), do not focus on it right now. Steps give weight loss, which is your main goal, and should not be sacrificed for resistance exercise if time for both is short.
Focus on exercises that work large muscle groups like the back, abdomen and legs.
While doing resistance exercise, do it at a pace that increases your heart rate a bit if your doctor says it is OK. Getting your heart rate up is a sign you are going at a pace that will help you burn more calories, which will help more weight weight loss.
Resistance exercise may be most helpful towards the end of your weight loss journey when you have lost a lot of weight or are trying to maintain your weight loss. In the beginning when you have obesity, your weight-bearing joints are already under a lot of stress. Resistance exercise can lead to injuries when you have obesity.