Design Pattern to only return certain variables of an object

Let's say I have the following class, with many instance variables and corresponding getters and setters:

public class Foo {
  private String a;
  private int b;
  ...
  private List<String> z;

  public String getA() { return a; }
  public void setA(String a) { this.a = a; }
  public int getB() { return b; }
  public void setB(int b) { this.b = b; }
  ...
}

There is another class that populates the values, and it's resource intensive:

public class MyService {

    public Foo retrieveFoo() {
        // call some resource intensive code to retrieve the values
        String a = getTheString();
        int b = getTheInt();
        List<String> z = getTheList();

        Foo f = new Foo();
        f.setA(a);
        f.setB(b);
        ...
        f.setZ(z);

        return f;
    }

}

I have multiple clients that want to use instances of the above class, but some are only interested in getting a small subset of the variable values and not everything:

public class ClientA {
    private MyService service;

    public void doSomething() {
        Foo f = service.retrieveFoo();
        String a = f.getA();
        int b = f.getB();
        // not interested in anything else
    }
}

 public class ClientB {
    private MyService service;

    public void doSomething() {
        Foo f = service.retrieveFoo();
        List<String> z = f.getZ();
        // not interested in anything else
    }
}

One thing I could do is have the client tell the MyService to only retrieve which values it's interested in. Something like this:

public class ClientA {
    private MyService service;

    public void doSomething() {
        // the Service would only retrieve a and b, which 
        // means all other variables would be set to Null
        Foo f = service.retrieveFoo(Arrays.asList("a","b"));
        String a = f.getA();
        int b = f.getB();
        // not interested in anything else
    }
}

However, this just seems wrong since the other values would be null. Is there a better way to design this?