Profile field create and set default value programmatically
Try with this 

$field_instance = array(                                      
'field_name'    =&gt; $fielddef['field_name'],               
'type'          =&gt; 'list_boolean',                        
'entity_type'   =&gt; 'user',                                
'bundle'        =&gt; 'user',                                
'label'         =&gt; t($opts['label']),                     
'description'   =&gt; t($opts['description']),               
'required'      =&gt; FALSE,                                 
'widget'        =&gt; array(                                 
    'type'      =&gt; 'options_onoff',                       
    'weight'    =&gt; 10,                                    
),                                                        
'settings'      =&gt; array(                                 
    'allowed_values' =&gt; drupal_map_assoc(range(0,1)),     
    'default_value' =&gt; array(1),         
)                                                         


);