You can wait until you lose weight to buy your life insurance, or purchase life insurance now and ask for a re-rate of your policy after you have lost the weight.
If you are overweight , they might charge you a higher premium.
If you are underweight , they may not issue the life insurance policy. or charge you more premium.
As long as your weight is within the average there is no problem.
Life insurance companies use a scale of height-to-weight ratio to determine the risk and how much they may add to your premium based on your weight.
Here's how you can compare life insurance quotes online from multiple highly-rated life insurance companies to find out which insurers may offer you the most affordable plans.