Training for a marathon and trying to lose weight quickly can pull in opposite directions. More running raises recovery demands; aggressive food restriction removes the energy needed to meet them. Decide which goal matters most right now instead of expecting every long run to produce a lower number on the scale.
Separate progress from daily weight
Body weight can fluctuate with fluids, stored carbohydrate and digestive contents. One weigh-in after a hot run says little about fat loss. Track your ability to complete suitable training, recover and sleep, as well as longer-term measurements if they are useful to you. Do not reward dehydration as progress.
Watch for under-fuelling
Persistent tiredness, poor recovery, declining performance and repeated injuries can be warning signs of insufficient energy, although they can have other causes. Relative energy deficiency in sport can affect men as well as women. These symptoms deserve assessment, not a stricter meal plan or more cardio.
Choose a sustainable phase
If finishing a marathon is the priority, make adequate fuelling and recovery central to the training block. If weight management is the main goal and you are new to exercise, a manageable walking and strength routine may be a more appropriate starting point. A dietitian or clinician can help when medical conditions, a history of disordered eating or repeated injuries are involved.
Use tracking to notice patterns
Record meals honestly and compare how you feel across training weeks. Do not blindly subtract an estimated watch calorie number or keep cutting food when training deteriorates. FitGeek can organise meals and check-ins, but its general targets do not diagnose low energy availability. Seek help for persistent symptoms and leave enough flexibility to reduce training or postpone the race.