Refer to figure.
During a turn, the balance of forces acting on an aircraft is altered to maintain the turn and ensure coordinated flight. The key forces involved are lift, weight, thrust, and drag. Here's how each force is affected:

Lift - Increased Lift: In a level turn, the aircraft must generate additional lift to counteract both its weight and the centripetal force needed to turn. The total lift vector is tilted to provide the necessary horizontal component to pull the aircraft into the turn.

To generate this increased lift, the pilot typically increases the angle of attack by pulling back on the control stick or yoke, which also increases the load factor (g-forces) on the aircraft.

Weight - Constant Weight: The weight of the aircraft remains constant and acts vertically downward through the aircraft's center of gravity.

During a turn, the weight continues to act towards the center of the Earth, but the aircraft’s path changes direction, necessitating adjustments in lift to maintain altitude.

Centrifugal Force - Horizontal Lift Component: For the aircraft to turn, a horizontal component of lift acts as the centripetal force, pulling the aircraft towards the center of the turn. This is achieved by banking the aircraft, which tilts the lift vector.

The centripetal force needed to maintain a circular path is proportional to the square of the aircraft's velocity and inversely proportional to the radius of the turn.

Thrust and Drag - Thrust Adjustments: To maintain airspeed during the turn, the pilot may need to adjust thrust. Increased drag due to higher angle of attack and bank angle requires more thrust to keep the airspeed constant. In steep turns, the engine power may need to be increased to overcome the additional drag and to maintain level flight.

Increased Drag: As the angle of attack increases to produce the additional lift, induced drag also increases. The aircraft experiences more drag during a turn compared to straight and level flight at the same speed.

Load Factor - Increased Load Factor: The load factor (or g-force) increases during a turn due to the additional lift required. The load factor is the ratio of the total lift to the aircraft's weight. In a coordinated turn, the load factor increases as the bank angle increases. For example, in a 60-degree banked turn, the load factor is 2, meaning the aircraft experiences forces equivalent to twice its weight.

Therefore, lift force must increase to compensate for the sum of centrifugal and gravitational force.