You can’t. However careful choices can modify your risk. Your breasts will always change as you get older, and this is irrespective of whether you have breast implants or not. This is because of biological changes that occur with ageing: loss of elastin, stretching of collagen, atrophy of breast tissue, loss of skin elasticity, sun damage to skin, smoking related damage, effects of weight change on skin and breast tissue, effects of pregnancies and breast feeding on skin and breast tissue, hormonal changes, weight of breast tissue and any implant’s weight and size (if placed). Large breast implants also stretch the tissue, acting a little like tissue expanders.
The biodimensional assessment goes some way to reducing excessive implant sizes being chosen by patients. You should very much speak to Mr Turton about this. If you do have implants after mastopexy, the larger the implant the greater the long term detrimental effects. This is because of the additional weight, and the compressive force of the implant on the surrounding tissues, which become thinner, and more stretched. In general you are better to avoid very large augmentations (eg over 350cc) and implant sizes that exceed your natural dimensions. Sub muscular breast implant augmentation may provide additional coverage to the implant but there are some negative aspects of sub-muscular positioning too and you sometimes have to trade-off one thing for another.
Wearing a well-fitting bra after your recovery is important (usually from 6-weeks). An underwire bra is safe and recommended. Wearing a comfortable sports bra at night is also very useful. A shock-absorber type bra should be worn during sport. Keeping the skin over the breasts moisturised helps to maintain the elasticity (bio oil is possibly advantageous here). Avoid the use of sunbeds and do not smoke at all (both have a very detrimental effect on skin elasticity and quality, as well as micro-vessel blood flow). Maintain your weight in the healthy range for your body mass index. Don’t sleep on your front at night. If you have children/further children, after breast augmentation, you breasts will very likely develop some sag.