You're certainly correct in your assumption that you cannot outwork a poor diet, not least when it comes to exercising heavily, edt333. When you got on your bike three years ago what changes did you make at the time, to allow you to begin losing weight?
The reason I ask is that the 70lbs you'd shed won't have been achieved through exercise alone; you'll have no doubt made the necessary alterations to your diet and your daily calorie intake to allow you to begin losing weight.
Equally, since whatever you were doing appeared to be working for you, I'm slightly confused as to why you'd begin to consume excessive amounts of protein and fat. Did your habits change as a result of concessions from medical and health organisations, over how they'd mis-informed the public for decades on the consumption of a low fat/high carb diet?
If so, what may have been reported in the media following these concessions, needs to be taken with a pinch of salt (no pun intended), largely due to the fact that high amounts of saturated fat in the diet do remain largely unhealthy, since it is simply stored around muscles and internal organs, to be utilised as energy in the future.
Granted, an excess of sugar in the diet also contributes towards stored fat, since your muscles will only absorb the glycogen needed to replenish depleted stores (through exercise, for example). Furthermore, the vast majority of what has been reported in the media is aimed at those who are obese or morbidly obese (already possessing metabolic conditions), in an attempt to make them change their eating habits from high sugar/high fat diets.
However, for those who exercise regularly, carbs (with a low sugar content) do remain an important food source as consumption immediately after exercise, in particular, helps to deliver glycogen to depleted muscle, allowing the body to re-fuel. Why do you think that distance runners and cyclists continually consume carbohydrate to fuel their endeavour?
Protein also plays an important role in the re-building of muscle, ensuring that existing mass isn't lost through cardiovascular endeavour. However, it is broken down by the body into amino acids, which enter the cells of the muscle to support growth and re-generation of fibres. Amino acids aren't utilised by the body to replace depleted glycogen reserves; glycogen can only largely be obtained from consumption of carbohydrate (preferably complex sources).
The purpose of the above is to hopefully allow you to understand that carbohydrate isn’t the enemy that it’s purported to be. After all, along with protein and healthy fats, carbohydrate is a macro-nutrient, one which is needed by the body, not least in terms of energy production. The real enemy is the excessively high levels of refined (sugary) carbohydrates present in 21st Century diets (cakes, sweets, pastries), as they’re hugely energy dense whilst offering very little in terms of nutritional value.
In light of changing dietary advice, it’s understandable that you’re confused, edt333. However, since the vast majority of your exercise appears to be dominated by cardio, if you’ve shunned the carbs in the past 12 months, I’d recommend that you re-introduce them, whilst reducing your fat intake, since I suspect that you’re attempting to replace fat with carbs in order to fuel your endeavour. As for your protein consumption, keep it around 1g/per lb of body weight, to ensure mass isn’t lost through gluconeogenesis (conversion of amino acids into glucose).
Additionally, in your quest to begin shedding the pounds again, research BMR calculators, since they’re largely accurate, in terms of determining your recommended daily calorific intake based upon your activity levels, so long as you’re eating a healthy, balanced diet. Having obtained your recommended BMR, you can then make the necessary daily calorie reductions which, combined with your mountain biking, allowing you to begin losing weight again.
