This means that though many weight-loss interventions suggest walking as the primary form of physical activity, it is probably too hard for many people.
In all actions concerning children, non-discrimination and the best interest of the child should be primary considerations and the views of the child given due weight.
So as far as the Middle East and Central Asia are concerned, a primary lesson of the Cold War relates to the relative weight the US can securely place in its alliance with Israel on the one hand, and its alliance with the Saudis on the other.
The invention of a superior harness enabled a horse to pull loads of far greater weight for longer periods of time, making the horse the primary farm animal.