Simple solution: olive oil. Nothing wrong with cereal, bacon or Subway. No need for casein before bed, no need for any changes at all to your diet - just add two ounces (4 tablespoons) of olive oil to your day and you'll gain. You could toss a tablespoon or two into a protein shake, and drizzle the rest on a salad. Your calories at 2700-2800 are what my middle-aged, 175 lb husband maintains on. You're just not eating enough.
PS some broccoli would do your colon some good. (Plus it fights estrogen

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Don't fear butter - it's good on the broccoli and it's healthy, testosterone-building calories. The olive oil is, too. It helps your boys turn cholesterol into testosterone.