Is it harder to lose weight after BBL?

This question of weight gain as it relates to BBL is fast becoming one of the most commonly posted questions in the RealSelf community. While it is true BBL is a weight sensitive procedure (in the sense that you need fat to achieve your result), it is never a good idea to pursue short term changes for surgery.
While there is no absolute number (lbs.) in terms of weight for undergoing liposuction with autologous fat transfer, the optimal candidate has reached a healthy and stable weight (preferably with a BMI less than 30, which is associated with a lower incidence of complications).
Potential candidates should also have adequate fat reserves for transfer. This becomes especially important when one considers the anticipated rate of fat resorption and graft loss. I typically recommened patients aim for at least 500 cc transferred per cheek. This would amount to 1 liter of fat (not lipoaspirate) after processing. Candidates with inadequate fat reserves are likely to be disappointed with their ultimate volume once healing is complete. 
With regards to your specific question, the difficulty or ease with which one loses weight will vary from one patient to the next. The real question is whether you should lose the weight post-op. I have found that patients who purposely gain weight before surgery will either struggle to lose weight post-op or will lose it in the grafted area post-operatively. Remember grafted fat will behave just as if it had never been grafted. If you gain weight for transfer, and lose the weight post-op, you are likely to lose your result. I would not change your weight for the sake of surgery. If you have reached a healthy stable weight (preferably with a BMI less than 30), the focus should be on maintaining.  
Ultimately, the question of "enough" fat is relative to your expectations. Do you have enough fat to undergo fat transfer? Based upon your photos, yes. Do you have enough to realize your goals? That is the question.
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

Losing weight will be as easy or as difficult as it is for you now.  BBL only changes the places where your fat is .  An Usually , after Liposuction , if you loose weight , you will loose it form the areas that didn't get lipo , or that still have more fat.  The first post op recovery weeks , your metabolism will be accelerated , so if you eat right , you ,ay loose some unwanted weight . Best wishes