Have you tried live ghost shrimp or grass shrimp (freshwater or saltwater)? Those will have at least a little more nutritional value than the live brine. Large copepods or amphipods would also be a good option. Soaking foods in garlic extract can help make it more enticing. The live brine has about zero nutrition, which is probably why he is getting thin. If he really won't eat any other foods, you can enrich the brine by putting the enrichment in the water and allowing the brine to filter feed on it for a while. Tube feeding is also an option if your SH has gone 3 or 4 days without eating. Also: What species do you have? Where and when did you get him? CB or WC? What are your water parameters (temperature, ammonia, nitrite, nitrate, pH)? Is he showing any other signs of a problem?
